Patent Publication Number: US-2020298530-A1

Title: Sensor device, method of manufacturing sensor device, and vehicle seat

Description:
CLAIM OF PRIORITY 
     This application is a Continuation of International Application No. PCT/JP2018/044077 filed on Nov. 29, 2018, which claims benefit of Japanese Patent Application No. 2017-241148 filed on Dec. 15, 2017. The entire contents of each application noted above are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sensor device, a method of manufacturing the sensor device, and a vehicle seat equipped with a sensor device. 
     2. Description of the Related Art 
     A known device contactlessly detects a motion or electric phenomenon of a live body by using an electrode disposed near the live body. In Japanese Unexamined Patent Application Publication No. 2013-188277, for example, an electrode device is described that is disposed at a vehicle seat or the like and performs electrocardiogram measurement. 
     SUMMARY OF THE INVENTION 
     In the electrode device described in Japanese Unexamined Patent Application Publication No. 2013-188277, an electrode and insulating body are formed from a woven fabric or knitted fabric having stretchability and air permeability to suppress a feeling of discomfort in touch and a feeling of stuffiness when the electrode device is used at a vehicle seat or the like. 
     However, when the insulating body is formed from a woven fabric or knitted fabric, if part of the fabric ravels, the ravel easily expand to the periphery thereof. The insulation property decreases at the raveled portion. This may lead to a problem in detection performance. 
     In view of this, one aspect of the present disclosure provides a sensor device that can suppress a decrease in an insulation property for electrodes while maintaining air permeability and flexibility, a method of manufacturing the sensor device, and a vehicle seat using such sensor devices. 
     According to one aspect of the present disclosure, a sensor device that has an insulative non-woven fabric and a conductive fabric forming an electrode is provided. The conductive fabric is joined to one surface of the non-woven fabric by at least one of fusion and seaming. 
     One aspect of the present disclosure can provide a sensor device that can suppress a decrease in an insulation property for electrodes while maintaining air permeability and flexibility, a method of manufacturing the sensor device, and a vehicle seat using such sensor devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of a vehicle seat equipped with sensor devices according to an embodiment of the present disclosure; 
         FIG. 2  illustrates an example of a sensor device according to a first embodiment; 
         FIG. 3A  illustrates an example of a method of manufacturing the sensor device in  FIG. 2 ; 
         FIG. 3B  illustrates the example of the method of manufacturing the sensor device in  FIG. 2 ; 
         FIG. 3C  illustrates the example of the method of manufacturing the sensor device in  FIG. 2 ; 
         FIG. 4A  illustrates the example of the method of manufacturing the sensor device in  FIG. 2 ; 
         FIG. 4B  illustrates the example of the method of manufacturing the sensor device in  FIG. 2 ; 
         FIG. 5  illustrates an example of a sensor device according to a second embodiment; 
         FIG. 6A  illustrates an example of a method of manufacturing the sensor device in  FIG. 5 ; 
         FIG. 6B  illustrates the example of the method of manufacturing the sensor device in  FIG. 5 ; 
         FIG. 6C  illustrates the example of the method of manufacturing the sensor device in  FIG. 5 ; 
         FIG. 7A  illustrates the example of the method of manufacturing the sensor device in  FIG. 5 ; 
         FIG. 7B  illustrates the example of the method of manufacturing the sensor device in  FIG. 5 ; 
         FIG. 7C  illustrates the example of the method of manufacturing the sensor device in  FIG. 5 ; 
         FIG. 8A  illustrates the example of the method of manufacturing the sensor device in  FIG. 5 ; 
         FIG. 8B  illustrates the example of the method of manufacturing the sensor device in  FIG. 5 ; 
         FIG. 9  illustrates an example of a sensor device according to a third embodiment; 
         FIG. 10A  illustrates an example of a method of manufacturing the sensor device in  FIG. 9 ; 
         FIG. 10B  illustrates the example of the method of manufacturing the sensor device in  FIG. 9 ; 
         FIG. 10C  illustrates the example of the method of manufacturing the sensor device in  FIG. 9 ; 
         FIG. 11A  illustrates the example of the method of manufacturing the sensor device in  FIG. 9 ; 
         FIG. 11B  illustrates the example of the method of manufacturing the sensor device in  FIG. 9 ; 
         FIG. 11C  illustrates the example of the method of manufacturing the sensor device in  FIG. 9 ; 
         FIG. 12A  illustrates the example of the method of manufacturing the sensor device in  FIG. 9 ; 
         FIG. 12B  illustrates the example of the method of manufacturing the sensor device in  FIG. 9 ; 
         FIG. 13A  illustrates an example of a sensor device according to a fourth embodiment; 
         FIG. 13B  illustrates the sensor device in  FIG. 13A , in a state in which the electrode cover is not illustrated; and 
         FIG. 14  illustrates one variation of a sensor device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to the drawings. 
       FIG. 1  illustrates an example of a vehicle seat  1  equipped with sensor devices  2  according to an embodiment of the present invention. In the example in  FIG. 1 , the vehicle seat  1  has a backrest  1 A and a seat  1 B. A plurality of sensor devices  2  are provided inside the surfaces of the backrest  1 A and seat  1 B. The vehicle seat  1  may have a function for blowing air to be used for temperature adjustment from, for example, the surface of the backrest  1 A or seat  1 B. In this case, since the sensor device  2  according to this embodiment has air permeability, the sensor device  2  does not hinder a flow of air. Therefore, the sensor devices  2  can be provided at appropriate positions in the backrest  1 A and seat  1 B without affecting the temperature adjustment function, so the sensor device  2  can detect information about a live body (such as a change in the motion of the body and an electric signal generated by the live body) with good sensitivity. 
     The sensor device  2  may have an electrode cover that faces the outside of the vehicle seat  1  and is made of a non-woven fabric having a color similar to the color of the outer surface of the vehicle seat  1 , as will be described later. Since this electrode cover covers the electrodes (formed from a conductive fabric), it is possible to prevent the electrodes from being noticeable from the outside. 
     Sensor devices according to embodiments of the present invention will be described below. 
     First Embodiment 
       FIG. 2  illustrates an example of a sensor device  2 A according to a first embodiment, illustrating an example of the outside shape of the sensor device  2 A when viewed from directions toward the front, side, and back. The sensor device  2 A illustrated in  FIG. 2  has conductive fabrics  21  and  22 , each of which forms an electrode, an insulative non-woven fabric  31 , and a substrate  10 . 
     An example of the conductive fabrics  21  and  22  is a fabric that is formed from chemical fibers such as polyester fibers, the surface of which is coated with a metal (conductor) such as copper or nickel. Another example is a fabric that is formed from a fabric material including a conductive material (such as carbon). Conductive fabrics  23  to  27  in embodiments described later are also formed from a material similar to the material for the conductive fabrics  21  and  22 . 
     The non-woven fabric  31  is a sheet-like member with insulative fibers intertwined and spread like a plane. The non-woven fabric  31  is formed from, for example, synthetic fibers such as polyester fibers or polyimide fibers or inorganic fibers such as glass fibers. Non-woven fabrics  33  to  37  in embodiments described later are also formed from materials similar to the material for the non-woven fabric  31 . 
     The two conductive fabrics  21  and  22  face each other with the non-woven fabric  31  located in between. The conductive fabric  21  is joined to the surface of the non-woven fabric  31  on the front side, and the conductive fabric  22  is joined to the surface of the non-woven fabric  31  on the back side. The joining of the conductive fabrics  21  and  22  to the non-woven fabric  31  is performed by, for example, fusion or seaming. In joining by fusion, heat or vibration is applied to a place of joining or the place is illuminated with a laser beam, in a state in which the conductive fabrics  21  and  22  and non-woven fabric  31  are overlaid on each other, for example. In joining by seaming, an insulative thread such as, for example, a synthetic fiber is used to sew the conductive fabric  21  and non-woven fabric  31  together and sew the conductive fabric  22  and non-woven fabric  31  together. 
     In  FIG. 2 , P 1  indicates a place of joining between the conductive fabric  21  and the non-woven fabric  31 , and P 2  indicates a place of joining between the conductive fabric  22  and the non-woven fabric  31 . As illustrated in  FIG. 2 , there is preferably a displacement in a plan view of the sensor device  2 A between the joining place P 1 , where the conductive fabric  21  is joined to the non-woven fabric  31 , and the joining place P 2 , where the conductive fabric  22  is joined to the non-woven fabric  31 . That is, the joining place P 1  and joining place P 2  are not overlaid on each other. 
     As illustrated in  FIG. 2 , most of the overlaid portion between the conductive fabrics  21  and  22  is included inside the outer edges of the conductive fabric  22  in a plan view of the sensor device  2 A. That is, the conductive fabric  21  as a whole is smaller than the conductive fabric  22 , and most of the conductive fabric  21  is included in the area of the conductive fabric  22  in a plan view. The joining place P 2  between the conductive fabric  22  and the non-woven fabric  31  partially encloses the circumference of the conductive fabric  21  in a plan view. 
     As illustrated in  FIG. 2 , the outer edges of the conductive fabric  21  and the outer edges of the conductive fabric  22  are separated from each other in a plan view of the sensor device  2 A in a state in which part of at least one surface (surface on the front side or surface on the back side) of the non-woven fabric  31  interposed between the conductive fabrics  21  and  22 . That is, the outer edges of the conductive fabric  21  and the outer edges of the conductive fabric  22  are preferably distant from each other in a direction along the surface of the non-woven fabric  31 . 
     The substrate  10  includes an electronic circuit connected to the two conductive fabrics  21  and  22 . This electronic circuit includes an amplifier circuit and the like. The amplifier uses one electrode (conductive fabric  21 , for example) as a detection electrode and amplifies an electric signal entered due to capacitive coupling between the detection electrode and a live body. In this case, the other electrode (conductive fabric  22 , for example) functions as a shield electrode controlled so as, for example, to have the same potential as the detection electrode. Alternatively, the electronic circuit of the substrate  10  may be a circuit that detects a change in capacitance (mutual capacitance) formed by the two electrodes (conductive fabrics  21  and  22 ). In this case, the electronic circuit detects a minute motion of the live body in response to the change in capacitance. The conductive fabrics  21  and  22  are connected to wiring patterns on the substrate  10  by, for example, soldering. 
       FIGS. 3A to 3C, 4A, and 4B  illustrate an example of a method of manufacturing the sensor device  2 A illustrated in  FIG. 2 . 
       FIG. 3A  illustrates a state in which nothing is attached to the non-woven fabric  31 . In this state in  FIG. 3A , the conductive fabric  21  is disposed on the surface of the non-woven fabric  31  on the front side as illustrated in  FIG. 3B , and the non-woven fabric  31  and conductive fabric  21  are preferably joined together by at least one of fusion and seaming as illustrated in  FIG. 3C . 
     After that, the conductive fabric  22  is disposed on the surface of the non-woven fabric  31  on the back side as illustrated in  FIG. 4A , and the non-woven fabric  31  and conductive fabric  22  are preferably joined together by at least one of fusion and seaming as illustrated in  FIG. 4B . At this time, as the joining place P 2  between the non-woven fabric  31  and the conductive fabric  22 , a place is selected where the place does not overlay the joining place P 1  between the non-woven fabric  31  and the conductive fabric  21  and where the conductive fabric  21  is not located. 
     As described above, with the sensor device  2 A in this embodiment, electrodes are formed by the conductive fabrics  21  and  22 , the conductive fabric  21  being joined to the surface of the insulative non-woven fabric  31  on the front side, the conductive fabric  22  being joined to the surface of the insulative non-woven fabric  31  on the back side. Therefore, air permeability and flexibility can be assured. The conductive fabrics  21  and  22  and the non-woven fabric  31  are joined together by at least one of fusion and seaming, making it difficult for air permeability or flexibility to be impaired. Furthermore, since the non-woven fabric  31  does not easily cause a ravel unlike a woven fabric and knitted fabric, it is possible to effectively suppress a decrease in the insulation property of the conductive fabrics  21  and  22 , each of which forms an electrode. In addition, since the porosity (density of clearances) of the non-woven fabric  31  is easily adjusted when compared with woven work and knitted work, a tradeoff between air permeability and the insulation property can be appropriately set depending on the use situation or the like. 
     With the sensor device  2 A in this embodiment, there is a displacement in a plan view of the sensor device  2 A between the joining place P 1 , where the conductive fabric  21  is joined to the non-woven fabric  31 , and the joining place P 2 , where the conductive fabric  22  is joined to the non-woven fabric  31 . Therefore, the conductive fabrics  21  and  22  can be stably insulated from each other. 
     With the sensor device  2 A in this embodiment, the outer edges of the conductive fabric  21  and the outer edges of the conductive fabric  22  are distant from each other in a direction along a surface (surface on the front side or surface on the back side) of the non-woven fabric  31 . Therefore, the conductive fabrics  21  and  22  can be more stably insulated from each other. 
     Second Embodiment 
       FIG. 5  illustrates an example of a sensor device  2 B according to a second embodiment. The sensor device  2 B illustrated in  FIG. 5  has conductive fabrics  23  and  24 , each of which forms an electrode, insulative non-woven fabrics  33  and  34 , and the substrate  10 . The substrate  10  in the sensor device  2 B is the same as the substrate  10  in the sensor device  2 A already described. This is also true for the substrate  10  in sensor devices  2 C and  2 D described later. Differences from the sensor device  2 A already described will be mainly described below. 
     The two conductive fabrics  23  and  24  face each other with the overlaid non-woven fabrics  33  and  34  located in between. The conductive fabric  23  is joined to the surface of the non-woven fabric  33  on the front side, and the conductive fabric  24  is joined to the surface of the non-woven fabric  34  on the back side. In  FIG. 5 , P 3  indicates a place of joining between the conductive fabric  23  and the non-woven fabric  33 , and P 4  indicates a place of joining between the conductive fabric  24  and the non-woven fabric  34 . In the example in  FIG. 5 , there is preferably a displacement in a plan view of the sensor device  2 B between the joining place P 3 , where the conductive fabric  23  is joined to the non-woven fabric  33 , and the joining place P 4 , where the conductive fabric  24  is joined to the non-woven fabric  34 . That is, the joining place P 3  and joining place P 4  are not overlaid on each other. 
     The surface of the non-woven fabric  33  on the back side is overlaid on the surface of the non-woven fabric  34  on the front side. In  FIG. 5 , Q 1  indicates a place of joining between the non-woven fabric  33  and the non-woven fabric  34 . As illustrated in  FIG. 5 , the joining place Q 1  between the non-woven fabric  33  to which the conductive fabric  23  is joined and the non-woven fabric  34  to which the conductive fabric  24  is joined is preferably positioned outside the areas of the conductive fabrics  23  and  24  in a plan view of the sensor device  2 B. 
     Joining between the conductive fabric  23  and the non-woven fabric  33 , joining between the conductive fabric  24  and the non-woven fabric  34 , and joining between the non-woven fabrics  33  and  34  are performed by fusion or seaming as with the sensor device  2 A already described. 
     As illustrated in  FIG. 5 , the outer edges of the conductive fabric  23  and the outer edges of the conductive fabric  24  are separated from each other in a plan view of the sensor device  2 B in a state in which part of at least one surface of the non-woven fabrics  33  and  34  (surface of the non-woven fabric  33  on the front side or surface of the non-woven fabric  34  on the back side) interposed between the conductive fabrics  23  and  24 . That is, the outer edges of the conductive fabric  23  and the outer edges of the conductive fabric  24  are preferably distant from each other in a direction along the surfaces of the non-woven fabrics  33  and  34 . 
       FIGS. 6A to 6C, 7A to 7C, 8A, and 8B  illustrate an example of a method of manufacturing the sensor device  2 B illustrated in  FIG. 5 . 
       FIG. 6A  illustrates a state in which nothing is attached to the non-woven fabric  33 . In this state in  FIG. 6A , the conductive fabric  23  is disposed on the surface of the non-woven fabric  33  on the front side as illustrated in  FIG. 6B , and the non-woven fabric  33  and conductive fabric  23  are preferably joined together by at least one of fusion and seaming as illustrated in  FIG. 6C . 
       FIG. 7A  indicates a state in which nothing is attached to the non-woven fabric  34 . In this state in  FIG. 7A , the conductive fabric  24  is disposed on the surface of the non-woven fabric  34  on the back side as illustrated in  FIG. 7B , and the non-woven fabric  34  and conductive fabric  24  are preferably joined together by at least one of fusion and seaming as illustrated in  FIG. 7C . 
     After that, the surface on the back side of the non-woven fabric  33  in the state illustrated in  FIG. 6C  and the surface on the front side of the non-woven fabric  34  in the state illustrated in  FIG. 7C  are overlaid on each other as illustrated in  FIG. 8A . When the non-woven fabrics  33  and  34  are placed in the overlaid state as illustrated in  FIG. 8A , the two conductive fabrics  23  and  24  face each other with the non-woven fabrics  33  and  34  located in between. The non-woven fabrics  33  and  34  placed in the overlaid state are preferably joined together by at least one of fusion and seaming as illustrated in  FIG. 8B . At this time, the non-woven fabrics  33  and  34  are joined together at positions outside the areas of the two conductive fabrics  23  and  24  in a plan view of the sensor device  2 B. 
     As described above, with the sensor device  2 B in this embodiment, the two opposing conductive fabrics  23  and  24  are separated from each other by the overlaid non-woven fabrics  33  and  34 . Therefore, the two conductive fabrics  23  and  24  can be stably insulated from each other. 
     With the sensor device  2 B in this embodiment, the non-woven fabric  33  to which the conductive fabric  23  on one side is joined and the non-woven fabric  34  to which the conductive fabric  24  on the other side is joined are joined together by at least one of fusion and seaming. Since the non-woven fabrics  33  and  34  are joined together as in joining between the conductive fabric  23  and the non-woven fabric  33  and joining between the conductive fabric  24  and the non-woven fabric  34 , manufacturing processes can be simplified. 
     With the sensor device  2 B in this embodiment, the non-woven fabric  33  to which the conductive fabric  23  is joined and the non-woven fabric  34  to which the conductive fabric  24  is joined are joined together outside the areas of the conductive fabrics  23  and  24  in a plan view of the sensor device  2 B. Therefore, the conductive fabrics  23  and  24  can be stably insulated from each other. 
     With the sensor device  2 B in this embodiment, there is a displacement between the joining place P 3 , where the conductive fabric  23  is joined to the non-woven fabric  33 , and the joining place P 4 , where the conductive fabric  24  is joined to the non-woven fabric  34 . Therefore, the conductive fabrics  23  and  24  can be stably insulated from each other. 
     With the sensor device  2 B in this embodiment, the outer edges of the conductive fabric  23  and the outer edges of the conductive fabric  24  are distant from each other in a direction along the surface of the non-woven fabric  33  on the front side and the surface of the non-woven fabric  34  on the back side. Therefore, the conductive fabrics  23  and  24  can be stably insulated from each other. 
     The structure, other than the above, of the sensor device  2 B according to this embodiment is similar to the structure of the sensor device  2 A already described, and the sensor device  2 B has an effect similar to the effect of the sensor device  2 A. 
     Third Embodiment 
       FIG. 9  illustrates an example of a sensor device  2 C according to a third embodiment. The sensor device  2 C illustrated in  FIG. 9  has conductive fabrics  25  and  26 , each of which forms an electrode, insulative non-woven fabrics  35  and  36 , and the substrate  10 . Differences from the sensor devices  2 A and  2 B already described will be mainly described below. 
     As illustrated in  FIG. 9 , the two conductive fabrics  25  and  26  face each other with the non-woven fabric  35  located in between, and the two non-woven fabrics  35  and  36  face each other. The conductive fabric  25  is joined to the surface of the non-woven fabric  35  on the front side, and the conductive fabric  26  is joined to the surface of the non-woven fabric  36  on the front side. In  FIG. 9 , P 5  indicates a place of joining between the conductive fabric  25  and the non-woven fabric  35 , and P 6  indicates a place of joining between the conductive fabric  26  and the non-woven fabric  36 . In the example in  FIG. 9 , there is preferably a displacement in a plan view of the sensor device  2 C between the joining place P 5 , where the conductive fabric  25  is joined to the non-woven fabric  35 , and the joining place P 6 , where the conductive fabric  26  is joined to the non-woven fabric  36 . That is, the joining place P 5  and joining place P 6  are not overlaid on each other. 
     The surface of the non-woven fabric  35  on the back side is overlaid on the surface of the non-woven fabric  36  on the front side, the conductive fabric  26  being joined to the surface of the non-woven fabric  36  on the front side. In  FIG. 9 , Q 2  indicates a place of joining between the non-woven fabrics  35  and  36 . As illustrated in  FIG. 9 , the joining place Q 2  between the non-woven fabric  35  to which the conductive fabric  25  is joined and the non-woven fabric  36  to which the conductive fabric  26  is joined is preferably positioned outside the areas of the conductive fabrics  25  and  26  in a plan view of the sensor device  2 C. 
     Joining between the conductive fabric  25  and the non-woven fabric  35 , joining between the conductive fabric  26  and the non-woven fabric  36 , and joining between the non-woven fabrics  35  and  36  are performed by fusion or seaming as with the sensor devices  2 A and  2 B already described. 
     As illustrated in  FIG. 9 , the conductive fabrics  25  and  26  as a whole are smaller than the non-woven fabric  35  in a plan view of the sensor device  2 C, and most of the conductive fabrics  25  and  26  are included in the area of the non-woven fabric  35  in a plan view. The outer edges of the conductive fabric  25  and the outer edges of the conductive fabric  26  are separated from each other in a state in which part of at least one surface (surface on the front side or surface on the back side) of the non-woven fabric  35  interposed between the conductive fabrics  25  and  26 , in a plan view of the sensor device  2 C. That is, the outer edges of the conductive fabric  25  and the outer edges of the conductive fabric  26  are preferably distant from each other in a direction along the surface of the non-woven fabric  35 . 
       FIGS. 10A to 10C, 11A to 11C, 12A, and 12B  illustrate an example of a method of manufacturing the sensor device  2 C illustrated in  FIG. 9 . 
       FIG. 10A  illustrates a state in which nothing is attached to the non-woven fabric  35 . In this state in  FIG. 10A , the conductive fabric  25  is disposed on the surface of the non-woven fabric  35  on the front side as illustrated in  FIG. 10B , and the non-woven fabric  35  and conductive fabric  25  are joined together by at least one of fusion and seaming as illustrated in  FIG. 10C . 
       FIG. 11A  illustrates a state in which nothing is attached to the non-woven fabric  36 . In this state in  FIG. 11A , the conductive fabric  26  is disposed on the surface of the non-woven fabric  36  on the front side as illustrated in  FIG. 11B , and the non-woven fabric  36  and conductive fabric  26  are joined together by at least one of fusion and seaming as illustrated in  FIG. 11C . 
     After that, the surface on the back side of the non-woven fabric  35  in the state illustrated in  FIG. 10C , and the surface on the front side of the non-woven fabric  36  in the state illustrated in  FIG. 11C  are overlaid on each other as illustrated in  FIG. 12A . When the non-woven fabrics  35  and  36  are placed in the overlaid state as illustrated in  FIG. 12A , the two conductive fabrics  25  and  26  face each other with the non-woven fabric  35  located in between. The conductive fabric  26  is in a state in which both surfaces of the conductive fabric  26  are covered by the two non-woven fabrics  35  and  36 . The non-woven fabrics  35  and  36  placed in the overlaid state are joined together by at least one of fusion and seaming as illustrated in  FIG. 12B . At this time, the non-woven fabrics  35  and  36  are joined together at positions outside the areas of the two conductive fabrics  25  and  26  in a plan view of the sensor device  2 C. 
     As described above, with the sensor device  2 C in this embodiment, the two opposing conductive fabrics  25  and  26  are separated from each other by the non-woven fabric  35 . Therefore, the two conductive fabrics  25  and  26  can be stably insulated from each other. Since the conductive fabric  26  is interposed between the two non-woven fabrics  35  and  36 , the insulation property for the conductive fabric  26  can be enhanced. 
     The structure, other than the above, of the sensor device  2 C according to this embodiment is similar to the structures of the sensor devices  2 A and  2 B already described, and the sensor device  2 C has an effect similar to the effect of the sensor devices  2 A and  2 B. 
     Fourth Embodiment 
       FIG. 13A  illustrates an example of a sensor device  2 D according to a fourth embodiment.  FIG. 13B  illustrates the sensor device  2 D illustrated in  FIG. 13A , in a state in which an electrode cover  41  is not illustrated. In the sensor device  2 D illustrated in  FIG. 13A , the surface, of the conductive fabric  25 , exposed to the outside in the already-described sensor device  2 C illustrated in  FIG. 9  (the surface is opposite to the surface in contact with the non-woven fabric  35 ) is preferably covered with the insulative electrode cover  41 . The other structure is almost the same as in the sensor device  2 C illustrated in  FIG. 9 . In the sensor device  2 D, however, the non-woven fabric  36  in the sensor device  2 C is replaced with a non-woven fabric  36 A, which is slightly larger in size than the non-woven fabric  36 . 
     The electrode cover  41  is preferably formed from an insulative non-woven fabric and is preferably joined to the non-woven fabric  36 A by fusion or seaming. Q 3  in  FIG. 13A  indicates a place where the electrode cover  41  and non-woven fabric  36 A are joined together. As illustrated in  FIG. 13A , the joining place Q 3  between the electrode cover  41  and the non-woven fabric  36 A is positioned outside the areas of the conductive fabrics  25  and  26 . 
     Since, in the sensor device  2 D according to this embodiment, the surface, exposed to the outside, of the conductive fabric  25  is covered with the electrode cover  41  formed from an insulative non-woven fabric as described above, the insulation property for the conductive fabric  25  can be enhanced. Since the non-woven fabric  36 A and electrode cover  41  are joined together as in joining between the conductive fabric  25  and the non-woven fabric  36  and joining between the conductive fabric  26  and the non-woven fabric  36 A, manufacturing processes can be simplified. 
     When the sensor device  2 D is disposed inside the vehicle seat  1  ( FIG. 1 ), the sensor device  2 D may be disposed so that the electrode cover  41  faces the outside of the vehicle seat  1  and the electrode cover  41  may have the same color as the outer surface of the vehicle seat  1 . Thus, since the conductive fabric  25  is covered with the electrode cover  41  that faces the outside of the vehicle seat  1  and that has the same color as the outer surface of the vehicle seat  1 , it is possible to make the conductive fabric  25  less likely to be noticeable from the outside and to make the electrode cover  41  itself less likely to be noticeable. 
     So far, sensor devices according to embodiments of the present invention have been described. However, the present invention is not limited only to the embodiments described above but various variations and modifications are possible without departing from the scope of the present invention. 
       FIG. 14  illustrates a variation of a sensor device according to an embodiment of the present invention. 
     A sensor device  2 E illustrated in  FIG. 14  has an insulative non-woven fabric  37  and a plurality of conductive fabrics  27 A to  27 F joined to one surface of the non-woven fabric  37  by fusion or seaming. On the surface of the non-woven fabric  37 , to which the conductive fabrics  27 A to  27 F are joined, wiring patterns  51 A to  51 F electrically continuous to the conductive fabrics  27 A to  27 F are preferably formed in advance. The wiring patterns  51 A to  51 F are formed on the surface of the non-woven fabric  37  by, for example, a film forming method such as sputtering. When the conductive fabrics  27 A to  27 F and the wiring patterns  51 A to  51 F formed on the surface of the non-woven fabric  37  in advance electrically are made continuous to each other in this way, it is unnecessary to connect these conductive fabrics to other wires such as electronic circuits by using connectors. Therefore, assembling processes can be simplified and the number of parts can be reduced. Since positions at which to dispose the conductive fabrics  27 A to  27 F on the surface of the non-woven fabric  37  are clear, work to position the conductive fabrics  27 A to  27 F is easy, making it possible to improve the efficiency of manufacturing. 
     Although, in  FIG. 1 , an example in which sensor devices  2  are disposed inside the vehicle seat  1  is illustrated, the present invention is not limited to this example. In another example of the present invention, sensor devices  2  may be disposed, for example, inside the lining (interior cover) of a vehicle. In this case, when an electrode cover that faces the outer surface side of the lining and has the same color as the outer surface of the lining is used, it is possible to make the conductive fabric covered with the electrode cover and the electrode cover itself less likely to be noticeable from the outside. 
     In the examples in the first to fourth embodiments described above, one conductive fabric is attached to each of the surface of a non-woven fabric on the front side and the surface thereof on the back side. However, a plurality of conductive fabrics may be attached to each surface of the non-woven fabric. The same number of conductive fabrics may be attached to the surface of a non-woven fabric on the front side and the surface thereof on the back side, or a different number of conductive fabrics may be attached to these surfaces. 
     The shapes and sizes of the conductive fabrics and non-woven fabrics and their positional relationships taken as examples in the first to fourth embodiments described above are merely examples, and may be appropriately changed. 
     This application claims priority based on Japanese Patent Application No. 2017-241148 filed on Dec. 15, 2017, and the entire contents of the Japanese Patent application are incorporated in this application by reference.