Abstract:
A seat belt device is provided. The seat belt device has a seat belt roller together with a locking device for locking the seat belt roller. The seat belt device furthermore has a guide pin which is moveably supported inside a guide link and is coupled to the locking device. The displacement of the guide pin inside the guide link depends on the direction of movement of the seat belt roller. The coupling of the pin to the locking device provides that locking of the seat belt roller is either brought about or prevented, according to the positioning of the guide pin in the guide link. The seat belt device makes it possible to ensure that seat belt locking is activated only when unreeling, and not when the set belt is being reeled in.

Description:
BACKGROUND  
         [0001]    The invention relates to a seat belt device.  
           [0002]    Seat belt devices having seat belt locks, which serve to lock the belt if it is unreeled jerkily are known. Such seat belt locks typically have a locking element, which engages with the frame of the seat belt device if the belt is unreeled jerkily.  
           [0003]    In such seat belt devices, however, uncontrolled engagement of the locking element in the frame of the seat belt device has also been observed in the event of a rapid belt return, i.e., the case of rapid belt reeling.  
           [0004]    Such seat belt devices typically comprise a large number of components, and thus are costly and expensive to design and-manufacture.  
           [0005]    A further disadvantage of such known seat belt devices is that they may exhibit poor response characteristics, i.e., both the engagement travel and engagement times prior to locking of the belt spindle are long.  
           [0006]    Furthermore, such seat belt devices often generate a high level of noise.  
         SUMMARY OF THE INVENTION  
         [0007]    One object of the present invention is to address one or more of these above-mentioned problems.  
           [0008]    According to an embodiment of the invention, a seat belt device for a vehicle having a seat belt is provided. The seat belt device includes a seat belt roller rotatably fixed to the belt frame of the vehicle for reeling and unreeling of the seat belt, a first locking device for locking the seat belt roller in relation to the belt frame of the seat belt, and a guide pin which is coupled to the locking device and which is moveably guided inside a guide link between a first position and a second position, the seat belt roller being locked in relation to the belt frame in the first position, and wherein locking of the seat belt roller in relation to the belt frame is prevented in the second position.  
           [0009]    According to an aspect of the invention, the guide pin serves to ensure that the seat belt roller locks only in the event of jerky unreeling of the belt, not in the event of jerky reeling. The guide pin may be moved into the first position or the second position according to the direction of rotation of the seat belt roller. Unwanted locking of the seat belt roller can thereby be prevented solely by means of the direction of rotation. In particular, the guide pin may be moved into the first position when the seat belt is being unreeled and into the second position when the seat belt is being reeled in.  
           [0010]    According to an aspect of the invention, shifting of the guide pin into the second position is preferably brought about by the moments of inertia of the first locking device and/or the guide pin occurring during the rotation of the seat belt roller. In this manner, the forces acting during rotation of the seat belt roller are utilized to bring about a movement of the guide pin into the second position.  
           [0011]    According to another aspect of the invention, the guide link may have some free travel in which the guide pin assumes the said second position. On assuming this position a change in the condition of the first locking device is generally prevented.  
           [0012]    According to another aspect of the invention, the guide link may run perpendicular to the axis of rotation of the seat belt roller. Arranging the guide link perpendicular to the axis of rotation allows the centrifugal forces generated during the rotation of the guide roller to be utilized to the fullest in shifting the guide pin into the second position. The guide link may comprise a longer link section and a shorter link section essentially perpendicular thereto, where the first position is situated at the end of the longer section opposite the junction of the sections, and the second position is situated at the end of the shorter section opposite the junction of the sections. The longer link section therefore serves to shift the guide pin into the first position, thereby locking the seat belt roller. The shorter link section serves to shift the guide pin into the second position, in which locking of the seat belt roller is prevented. The necessary forces are in both cases produced by rotation of the seat belt roller. Making the sections run perpendicular to one another provides that the forces needed for movement along the respective link sections are optimally decoupled from one another.  
           [0013]    According to an aspect of the invention, the seat belt device preferably also has a spring element, which holds the first locking device and the coupled guide pin in a rest position. This ensures that once the seat belt roller has come to a standstill, the guide pin does not remain at one of the ends of the link sections, but returns promptly to the rest position in the area of the junction of the two link sections. This guarantees reliable functioning even in the event of repeated, jerky reeling or unreeling of the seat belt at brief intervals.  
           [0014]    The spring element may comprise a coil spring or a spring clip.  
           [0015]    The first locking device may comprise a retaining pawl, which is capable of engaging in a frame of the seat belt device to lock the seat belt roller.  
           [0016]    The seat belt roller may also comprise the following additional features: a flange connected to the seat belt roller and the first locking device; a ratchet wheel rotatably fixed to the belt frame; and a second locking device, coupled to the ratchet wheel, for locking the ratchet wheel in the event of a jerky unreeling of the seat belt, wherein the guide link is provided in the ratchet wheel, and the guide pin, upon locking of the ratchet wheel, is moved along the guide link towards the first position by further rotation of the flange and wherein the first locking device, thereby causing the first locking device to lock the seat belt roller, and wherein the guide pin is moved towards the second position by jerky reeling in of the seat belt, thereby preventing the first locking device from locking the seat belt roller.  
           [0017]    The second locking device may comprise a retaining pawl, which engages in a toothing of a wheel rim should a predetermined angular acceleration of the seat belt roller in the belt unreeling direction be exceeded, such that the ratchet wheel is locked in relation to the seat belt roller, and the guide pin inside the guide link is moved into the first position in the event of further rotation of the seat belt roller in relation to the ratchet wheel.  
           [0018]    The seat belt device may also further comprise an inertial mass element capable of rotating in relation to the seat belt roller about the seat belt roller axis, wherein the guide link is provided in the inertial mass element, and the inertial mass element is rotated in relation to the seat belt roller, and the guide pin in the guide link is moved from the first position to the second position should a predetermined angular acceleration of the seat belt roller be exceeded.  
           [0019]    One advantage of embodiments of the invention is the requirement of fewer parts, so that the effort and cost of manufacture are reduced. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    The invention will now be explained on the basis of exemplary embodiments and with reference to the drawings, in which:  
         [0021]    [0021]FIG. 1 shows a diagrammatic cross-section through a part of a seat belt device;  
         [0022]    [0022]FIG. 2 shows a diagrammatic perspective view of the components of the part shown in FIG. 1;  
         [0023]    [0023]FIG. 3 shows a diagrammatic perspective view of further parts of a seat belt device according to a first exemplary embodiment of the invention;  
         [0024]    [0024]FIGS. 4, 5 and  6  show a diagrammatic top view of the parts shown in FIG. 3 in various states;  
         [0025]    [0025]FIGS. 7 and 8 in diagrammatic form show parts of a seat belt device according to a second exemplary embodiment of the invention; and  
         [0026]    [0026]FIG. 9 in diagrammatic form shows parts of a seat belt device according to a third exemplary embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0027]    [0027]FIG. 1 shows a diagrammatic cross-section through a force limiter for a seat belt system. FIG. 2 shows a perspective view of the components of the limiter. The force limiter comprises a rotatable spindle (or seat belt roller)  1  with a spindle bearing  2 , on which a seat belt (not shown) can be reeled and unreeled. A flange  3 , rotatable in relation to the spindle  1 , is arranged at one end of the spindle  1  situated along its axis of rotation. In addition, a first retaining pawl  4  is provided for arresting the flange in relation to a belt frame, should the seat belt be drawn out jerkily, for example.  
         [0028]    A torsion bar  5  is also provided, which has a toothed rim at both ends, by means of which the torsion bar  5  is anchored so that it cannot rotate in corresponding recesses of the spindle  1  and the flange  3  respectively. The torsion bar  5  couples the spindle  1  and the flange  3  together, so that when the limiter is at rest (for example, in the absence of an accident situation) the spindle  1  and the flange  3  can rotate together about an axis of rotation  7 , in order to reel the seat belt up on to the spindle  1  or to unreel it therefrom.  
         [0029]    [0029]FIG. 3 shows a diagrammatic perspective view of a ratchet wheel  10  and a wheel rim  11  of a seat belt device according to a first exemplary embodiment of the invention. The wheel rim  11  is mounted on the ratchet wheel  10  as indicated by the arrows. Alternatively, the ratchet wheel  10  may also be mounted on the wheel rim  11 .  
         [0030]    The wheel rim  11  is locked in relation to the belt frame, while the ratchet wheel  10  is rotatable in relation to the belt frame.  
         [0031]    The internal circumferential surface of the wheel rim  11  is provided with teeth  12 , with which a second retaining pawl  13  engages, if the seat belt is drawn out jerkily, for example. For this purpose the second retaining pawl  13  is supported so that it can rotate about an axis  14  arranged on the surface area of the ratchet wheel  10 . The axis  14  lies outside the center of the circular surface area of the ratchet wheel  10 . If the seat belt is drawn out jerkily, the retaining pawl  13  rotates about the axis  14  in opposition to the force of a spring  15 , so that the tip  16  of the second retaining pawl  13  engages with the teeth  12  of the wheel rim  11 .  
         [0032]    The ratchet wheel  10  is connected to the flange  3  by way of a helical extension spring (not shown). In normal operation the ratchet wheel  10  rotates at the same speed as the flange  3 . The rotational force is in this case transmitted by the helical extension spring. If the seat belt is drawn out jerkily, the second retaining pawl  13  rotates about the axis  14  and engages with the teeth  12  of the wheel rim  11 , as described above. The ratchet wheel  10  connected to the wheel rim  11  is therefore locked in relation to the belt frame. The flange  3  with the first retaining pawl  4  now continues to rotate together with the spindle  1  in opposition to the force of the helical extension spring.  
         [0033]    The first retaining pawl  13  is guided in the ratchet wheel  10  by means of a guide pin  20  in a guide link  18 . This guide is inoperative as long as the ratchet wheel  10  rotates together with the flange  3 . If the ratchet wheel  10  is locked in relation to the belt frame, however, the flange  3  together with the first retaining pawl  4  rotates further in relation to the ratchet wheel  10 . The first retaining pawl  4  consequently rotates in relation to the ratchet wheel  10 , the orientation of the first retaining pawl  4  during this relative rotation now being determined by the guide link  18 . Thus, the first retaining pawl  4  is brought into engagement with the frame of the seat belt device, and therefore prevents any further rotation of the flange  3  and of the spindle  1  connected thereto. The seat belt lock is therefore operative.  
         [0034]    [0034]FIG. 4 shows a diagrammatic front view of the ratchet wheel  10  with second retaining pawl  13  mounted on the axis  14 . An arrow  17  indicates how the tip  16  of the retaining pawl  13  moves outwards when a torque produced by the rotation of the seat belt roller and acting on the retaining pawl  13  is greater than the torque generated by the retaining force of the spring  15 .  
         [0035]    The guide link  18  can also be seen more clearly from FIG. 4. A guide pin  20 , which is connected to the first retaining pawl  4 , is guided inside the guide link  18 . FIG. 4 shows the guide pin  20  in its rest position. The first retaining pawl  4  and hence the guide pin  20  connected to the first retaining pawl  4  are held in the rest position by a spring element (not shown).  
         [0036]    [0036]FIG. 5 likewise shows a diagrammatic front view of the ratchet wheel  10 , the guide pin  20  here bearing on a radially outer stop  21  of the guide link  18 . Displacement of the guide pin  20  along the link  18  is brought about by locking of the ratchet wheel  10  in relation to the flange  3 , as described above. Due to the relative rotation of the flange  3  together with the first retaining pawl  4 , the guide pin  20  connected to the first retaining pawl  4  is displaced in relation to the ratchet wheel  10  along the guide link  18 , until the first retaining pawl  4  engages with the frame of the seat belt device and activates the belt lock.  
         [0037]    When the belt lock is released and the seat belt is being reeled in, the first retaining pawl  4  and hence also the guide pin  20  is moved back into the starting position shown in FIG. 4 by the spring force of the said spring element acting on the first retaining pawl  4 .  
         [0038]    Conversely, in the event of a rapid spindle movement in the reeling direction, i.e., anticlockwise in FIGS.  3  to  5 , the guide pin  20  moves in a free travel  22  (see FIG. 6) of the guide link  18 , owing to the centrifugal forces acting on the said pin and on the first retaining pawl  4  connected thereto. The free travel  22  means that the first retaining pawl  4  cannot engage in the frame during the reeling movement.  
         [0039]    As soon as the spindle  1  has come to rest again, the retaining pawl is moved into the starting position by way of the said spring element, so that the guide pin  20  also again assumes the rest position shown in FIG. 4.  
         [0040]    [0040]FIGS. 7 and 8 each show a part of a seat belt device according to a second exemplary embodiment of the invention. In this embodiment the ratchet wheel  10  and the wheel rim  11  are replaced by an inertial mass  25  in the form of a disk, which is rotatably supported on the spindle axis  26  and is indirectly held in its rest position by a biased spring element  27 . The spring element  27  is coupled to the spindle axis  26  on one end and to the guide pin  20  on the other end.  
         [0041]    Similar to the first embodiment, the guide pin  20  is coupled to the first retaining pawl  4  and guided in a guide link  18  in the inertial mass  25 .  
         [0042]    The spring element  27  is designed so that its spring force holds the first retaining pawl  4  and the inertial mass  25  in the rest position up to a defined angular acceleration. When the acceleration threshold is exceeded, the spindle  1  moves relative to the inertial mass  25 . As a result the guide pin  20  is displaced in the guide link  18  and the first retaining pawl  4  engages in the belt frame.  
         [0043]    This second embodiment has the advantage in that the number of components needed can be reduced, thereby reducing the costs. It requires only short engagement travel and time to locking of the spindle  1 . In addition, the noise generated by the first retaining pawl  4  is reduced.  
         [0044]    [0044]FIG. 9 shows a seat belt device according to a further exemplary embodiment of the invention. In this embodiment, the guide pin  20  is held in the rest position shown inside the guide link  18  by means of a spring clip  30 . The spring clip  30  prevents free movement of the guide pin and thereby of the first retaining pawl  4 , so that in addition to preventing unwanted locking of the spindle  1 , any unwanted rattling of the retaining pawl  4  or of the guide pin  20  is also prevented.  
         [0045]    The priority application, German Patent Application No. DE 102 36 858.9 filed Aug. 7, 2002, is hereby incorporated by reference herein in its entirety.  
         [0046]    Given the disclosure of the present invention, one versed in the art-would appreciate that there may be other embodiments and modifications within the scope and spirit of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims.