Patent Publication Number: US-2002000742-A1

Title: Vehicle seat sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001] The present invention is related to Japanese patent application No. 2000-195137, filed Jun. 28, 2000; the contents of which are incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002] The present invention relates to a vehicle seat sensor, and more particularly, to a vehicle seat sensor that has a flexible support.  
       BACKGROUND OF THE INVENTION  
       [0003] In a conventional vehicle seat sensor, a thin sensor mat is mounted to a passenger&#39;s seat between the seat cushion and trim cover (facing). This sensor detects the presence, absence and physique of an occupant sitting on the passenger&#39;s seat according to the weight of the occupant on the seat portion. However, since the seat cushion and the trim cover of the seat portion have large variations in surface condition and hardness, the seat sensor has large variations in detected outputs. Further, since the seat sensor is a thin mat, as described above, the seat sensor may be bent by the seated person. Also, mounting the seat sensor inside the seat portion may result in poor mounting-positioning accuracy.  
       SUMMARY OF THE INVENTION  
       [0004] The present invention provides a vehicle seat sensor which stabilizes the shape of a sensor mat by using a flexible and soft stabilizing member such as a foam sheet. A vehicle seat sensor includes a sensor mat positioned between a seat cushion and a trim cover of a seat portion, all parallel to the seating surfaces of the seat portion. A soft, flexible (and preferably smooth—such as a film material) stabilizing member is provided between the trim cover and the sensor mat. Here, the seat mat includes a plurality of sensor cells in matrix-like arrangement.  
       [0005] In another aspect, a sensor mat mounted between a seat heater and a seat cushion, parallel to the seating surface of the seat portion, and a soft, flexible (and preferably smooth—such as a film material) stabilizing member are provided between the trim cover and the sensor mat. Here, the sensor mat includes a plurality of sensor cells in matrix-like arrangement, and the seat heater is placed between the seat cushion and a trim cover of the seat portion of the vehicle seat. Further, the soft and flexible stabilizing member has heat insulating properties.  
       [0006] In another aspect of the invention, the vehicle seat sensor includes a second soft and flexible stabilizing member between the seat cushion and the shape stabilizing member.  
       [0007] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
     [0009]FIG. 1 is an exploded perspective view showing a seat sensor according to the present invention mounted inside a seat portion of a passenger&#39;s seat;  
     [0010]FIG. 2 is a sectional view taken along line  2 - 2  in FIG. 1; and  
     [0011]FIG. 3 is an exploded perspective view of the seat sensor according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0012] Hereinafter, the present invention will be described with reference to appended drawings. FIGS. 1 and 2 show a seat sensor S according to the present invention with a seat portion  10  of a vehicle passenger&#39;s seat. The seat portion  10  has a seat cushion  11 , a trim cover  12  for covering the seat cushion, and a seat heater  13  disposed between the trim cover and the seat cushion. The seat heater  13  heats the seat portion  10 .  
     [0013] As shown in FIGS. 1, 2, the seat sensor S is disposed between the seat heater  13  and the seat cushion  11  to be parallel to a seating surface (upper surface  12   a  of the trim cover  12 ). The seat sensor S is provided with a sensor mat  20 , and both flexible and soft stabilizing members  30 ,  40  for sandwiching the sensor mat  20  therebetween.  
     [0014] The sensor mat  20  preferably is made of a thin film, and is integrally formed with plural sensor cells  21  and a cell supporting portion  22  for supporting each sensor cell  21  (refer to FIG. 3). The cell supporting portion  22  is constructed by placing spacers between both resin films so that plural bars of strip portions  22   a , which are parallel to one another, are connected to each other at their ends. In FIG. 3, the sensor cells  21  are shown without the spacers between the resin films. The same number of sensor cells  21  are formed integrated with each strip portion  22   a  and are separated from each other. Thereby, sensor cells  21  are disposed over the seating surface of the seat portion  10  in matrix-like arrangement.  
     [0015] In a seat sensor  20  constructed in such a manner, the sensor cells  21  are pressed by the weight of an occupant sitting on the seating surface of the seat portion  10 , thereby detecting the weight. If a child seat is placed on the seating surface of the seat portion  10 , the seat sensor  20  detects the weight of the child seat.  
     [0016] Each of the stabilizing members  30 ,  40  is preferably formed of a soft and flexible heat insulating material having a thickness of preferably 1 to 30 mm. Such material can be a thin urethane foam. The stabilizing members  30 ,  40  are uniformly fixed to both surfaces of the sensor mat  20  by an adhesive. The outer surface of the stabilizing member  30  is positioned close to the rear surface of the seat heater  13 , and the outer surface of the shape stabilizing member  40  is proximate the surface of the seat cushion  11 . The seat sensor is provided with an electronic control unit  60  connected to each sensor cell  21  through a wire harness  50 . Detected output signals from respective sensor cells  21  are input to the electronic control unit  60  through the wire harness  50 , and the electronic control unit  60  determines the presence or absence of an occupant sitting on the seating surface.  
     [0017] In the present embodiment, the sensor mat is sandwiched between the film designed stabilizing members  30 ,  40 . Here, each of the shape stabilizing members  30 ,  40  is formed of a soft material such as thin urethane foam, as described above. Accordingly, both the shape stabilizing members  30 ,  40  flex and absorb shape variations and hardness of the seat cushion  11  and the trim cover  12 . That is, pressures and bending loads, transmitted to the sensor mat  20  from the seat cushion  11  and the trim cover  12 , can be made uniform through both the shape stabilizing members  30 ,  40 . This means that the shape of the sensor mat  20  is kept stabilized.  
     [0018] By improving the position accuracy of the seat sensor S inside the seat portion  10 , as described above, the seat sensor S can accurately detect the weight of the occupant sitting on the seating surface of the seat portion  10  in plane-like through each sensor cell  21 .  
     [0019] Since the shape stabilizing member  30  is placed between the seat heater  13  and the sensor mat  20 , as described above, the heat energy transmittance from the seat heater  13  to the sensor mat  20  can be interrupted by using the heat insulation properties of the shape stabilizing member  30 . Thereby, the temperature characteristics and durability of the sensor mat  20  of the seat sensor S are improved.  
     [0020] As a note, the seat heater  13  is not require and can be eliminated. Also, one of the shape stabilizing members  30 ,  40  can be eliminated. The material of the shape stabilizing members  30 ,  40  can be rubber sponge, non-woven fabrics, or fabrics or cotton other than urethane foam. Each of the shape stabilizing members  30 ,  40  can be formed so that holes are partly provided therein. The seat sensor can be generally mounted inside a seat portion of a vehicle seat without being limited to a passenger car.  
     [0021] While the above-described embodiments refer to examples of usage of the present invention, it is understood that the present invention may be applied to other usage, modifications and variations of the same, and is not limited to the disclosure provided herein.