Abstract:
A sensor mat, particularly for vehicle seats in connection with restraint systems, which includes at least one positioning strip that may be snapped onto a fastener.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a sensor mat, especially for passenger classification and/or passenger detection in connection with restraint systems. 
   BACKGROUND INFORMATION 
   Systems for passenger classification are used in the automotive field. These systems are based, among other things, on sensor mats that are connected with an evaluation electronics system, and that are built into the vehicle seat cushion. They supply an output signal that corresponds to the weight of the person on the seat, which is evaluated for the weight-dependent control of the restraint systems by the air bag control unit. When the seat is unoccupied, the triggering of the means of restraint is forestalled. 
   At this time, there are various methods to fix this sensor mat, when installing it in the seat cushion, in a setpoint position in such a way that it cannot slip out of place during the fixing on of the seat cover. This is important, since a sensor mat that has slipped out of place may lead to a wrong classification or to the triggering of means of restraint in the case of an unoccupied seat cushion. 
   Examples of fixing the sensor mat are described in German Patent Application No. DE 103 14 472. Thus, a sensor mat is fixed to the seat cushion foam by being adhered to it, using a double adhesive tape or adhesive strip, by being stuck to the seat cushion foam, using pins, such as fir cone pins, or by being fixed to the seat cushion foam by Velcro. 
   SUMMARY OF THE INVENTION 
   According to the present invention, the fixing aid positions a sensor mat, for example, for passenger classification and/or for passenger detection or other functional mats, reliably in a setpoint position, without the use of additional component parts, such as adhesive tape, pins, fir cone pins, etc. 
   Slipping out of place of the sensor mat/functional mat during the construction of the seat cushion is effectively avoided. 
   The fixing aid is achieved by the suitable geometrical design of the sensor mat and the devices already present in the seat cushion for fixing on the seat cover (such as wing clips). This clearly reduces the expenditure and, at the same time, gains in reliability, since slipping out of place becomes almost impossible. The appropriately designed sensor mat is snapped into the present device for fixing on the seat cover (e.g. wing clips) and is thereby positioned into the setpoint position. 
   In this context, the fixing is particularly precise, since the devices for fixing on the seat cover are fitted very accurately into the seat foam. 
   Owing to the fixing aid according to the present invention, no additional component parts such as adhesive tape, pins, fir cone pins, etc., are required for fixing. In contrast to an adhesive connection, the fixing created is detachable without damage to the sensor mat. This is particularly important in case of repairs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an image of a sensor mat. 
       FIG. 2  shows the seat foam of a vehicle seat having fastening means for the seat cover, which are also used for fastening the sensor mat. 
       FIG. 3  represents the fixing of the sensor mat to this seat foam. 
       FIG. 4  shows the fixing of a positioning strip of the sensor mat in a wing clip. 
   

   DETAILED DESCRIPTION 
   On the sensor mat there are provided positioning strips having suitable openings for snapping into place into the devices for fixing on the cover (e.g. wing clips). The openings in the positioning strips are formed in such a way that a secure snapping in is ensured, e.g. using the wing clips. The positioning strips are connected to the mat in such a way that the sensor mat is positioned in the setpoint position by snapping into, for instance, the wing clips. 
     FIG. 1  shows a sensor mat  10  which, in the embodiment shown, has two positioning strips  12  and  14 . The positioning strips are a part of sensor map  10 , in this instance. The positioning strips are stamped during the manufacturing of the sensor mat, which is also stamped, of the base material for the sensor mat, together with carrier structure  15  for the electrical parts. Electrical structures  13  are then printed onto the carrier structure of the sensor mat. Consequently, fitting measures, such as adhesion, etc., are not necessary. The positioning strips have openings  16 ,  18  that are formed in such a way that they snap into the fastening means in the assembly. In one embodiment, the fastening means are wing clips, so that the openings are circular, having dimensions that correspond to the wing clips. What is important is that the positioning strip snaps in with the assigned fastening means, so that detaching the strips is only possible with the application of considerable force, and coincidental detachment of the strips during normal operation of the seat is prevented. 
     FIG. 2  shows seat foam  20  of a vehicle seat having fastening means  22  for the seat cover. Fastening means  22  are wing clips, in this instance, by which the seat cover is fastened tightly (braced). They are also used for fixing and positioning the sensor mat. 
   This is depicted in  FIG. 3 . There, seat foam  20 , that is known from  FIG. 2 , is shown with fastening means  22 . Furthermore, a sensor mat  25 , having positioning strips  27 , has been laid onto the seat foam. Positioning strips  27  are snapped into fastening means  22 . This fixes sensor mat  25  in its setpoint position. In this context, not all available fastening means are used, but only as many as are necessary to fix the sensor mat. In one exemplary embodiment, three positioning strips are provided, which are plugged into three available fastening means. 
     FIG. 4  shows a cutout of  FIG. 3 , in which one positioning strip is shown snapped into a wing clip.  FIG. 4  shows seat foam  20 , sensor mat  25 , positioning strip  27  of sensor mat  25  as well as wing clip  22 . The positioning strip is formed from the base carrier of sensor mat  25 . Opening  30  of positioning strip  27  is formed in such a way that it is adapted to the dimensions of the wing clip. The wing clip is pressed through this opening in the positioning strip, and the sensor mat is snapped in this manner into its setpoint position. This is achieved in that the wing clip has at least one movable tab which, in the manner of a barb, prevents the positioning strip from detaching itself again in an independent manner. The opening in the positioning strip is essentially circular, and in this context, the circular diameter is slightly smaller than the dimensions of the fastening means when at rest, in order to avoid detachment in an independent manner; it is, however, big enough so that the flexibility of the material of the sensor mat and/or of the fastening means permits a snapping on of the positioning strip, using a slight force effort. 
   The positioning strip, in this context, is also formed in such a way that it fits into a recess in the seat foam. Furthermore, the positioning strip may be detached again by an appropriate force effort or by pressing the wing clip, without damaging the sensor mat.