Abstract:
A seating detecting device is comprised of a first cushion having an insert wire embedded therein, a second cushion placed on the first cushion, a surface sheet placed on the second cushion, a suspension wire fixed to the surface sheet and arranged between the surface sheet and the second cushion, and a pressure detecting device provided between an upper surface of the first cushion and a lower surface of the second cushion and having a plurality of through-holes for the suspension wire being fixed by the insert wire therethrough thereby to fix the surface sheet to the first and second cushions.

Description:
CROSS REFERENCE OF RELATED APPLICATION 
     This application is based on and claims priority under 35 U.S.C. §119 with respect to Japanese Application No. 2001-226608 filed on Jul. 26, 2001, the entire content of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     This invention relates to a seating detecting device. More particularly, the present invention pertains to a seating detecting device which detects a physique of a passenger and a shape of an object. 
     BACKGROUND OF THE INVENTION 
     A known device is disclosed in Japanese Patent Laid-Open Publication No.10-211836. As shown in FIG. 5, the known device includes a cushion  52 , a pressure sensitive switch  53  which is a flexible sheet contained under a recess  51 , and a resilient closure  54  which is in contact with a lower surface of the pressure sensitive switch  53 , closing the recess  51 . The recess  51  is opening toward a bottom which is located in the opposite side of a seating surface in the cushion  52 . 
     Because the known device is only aimed to detect whether a passenger is seated or not, the pressure sensitive switch  53  does not need a large area in a seating area. 
     However, in order to operate an air bag appropriately as a passenger protection device, an identification of an object on the seat has been needed. More specifically, a judgment of whether an item on the seat is a passenger or an object, and furthermore, if it is a passenger, an identification of a physique of the passenger is needed. In order to obtain such specific information about what is on the seat, a pressure detecting sensor which has a detection area in almost an entire seating area of a cushion is necessary. Also, the pressure detecting device needs to be disposed in a position which is close to a seating surface to assure a detection accuracy. 
     In addition, normally a seat for a vehicle is structured to fix a surface sheet in the cushion by fixing a suspension wire of the surface sheet with a wire which is embedded in the cushion with a fixing ring. Therefore, if a pressure detecting sensor is disposed in a position which is close to the seating surface, the pressure detecting sensor interferes with the suspension wire of the surface sheet. As a result, a shape of the pressure detecting sensor needs to be formed to avoid an interference with the suspension wire. However, because the suspension wire has various layout patterns in accordance with designs of seats, various forms of the pressure detecting sensor are needed in accordance with the layout patterns of the suspension wire. 
     Accordingly, it is an object of the present invention to provide a seating detecting device which has an area covering the entire seating surface to be applicable to various design seats. 
     SUMMARY OF THE INVENTION 
     According to the first aspect of the invention, a seating detecting device is comprised of a first cushion having an insert wire embedded therein, a second cushion placed on the first cushion, a surface sheet placed on the second cushion, a suspension wire fixed to the surface sheet and arranged between the surface sheet and the second cushion, and a pressure detecting device provided between an upper surface of the first cushion and a lower surface of the second cushion and having a plurality of through-holes for the suspension wire being fixed by the insert wire therethrough thereby to fix the surface sheet to the first and second cushions. 
     According to the second aspect of the invention, the seating detecting device is further comprised of a fixing member fixing the insert wire and the suspension wire. 
     According to the third and forth aspect of the invention, the seating detecting device is characterized in that the plurality of through-holes is arranged along a first direction and a second direction, and the first direction crosses the second direction. 
     According to the fifth and sixth aspects of the invention, the pressure detecting device includes a plurality of pressure detecting elements. 
     According to the seventh and eighth aspect of the invention, the second cushion includes a plurality of through-holes corresponding to the plurality of through-holes of the pressure detecting device. 
    
    
     BRIEF DESCRIPTION OF THE INVENTION 
     The foregoing and additional features and characteristics of the present invention will become more apparent from the following detained description considered with reference to the accompanying drawing figures in which like reference numerals designate like elements: 
     FIG. 1 is a plane view showing a portion of a sensor film  18  omitting a surface sheet  16  and an upper cushion  14  according to an embodiment of the invention; 
     FIG. 2 is a cross- sectional view taken along the line II—II shown in FIG. 1 of the seating detecting device  10  including the surface sheet and the upper cushion  14 ; 
     FIG. 3 is a plane view three patterns of a lower cushion  11  and a sensor film  18  of the seating detecting device  10  which are applied to three layout patterns of the suspension wire  15  according to the embodiment of the invention; 
     FIG. 4 is a plan view of the sensor film  18  of the seating detecting device  10  according to the embodiment of the invention; and 
     FIG. 5 is a cross sectional view of a seating detecting device  50  of a known art. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of this invention will be explained with reference to the attached drawings. 
     As shown in FIG.  1  and FIG. 2, a seating detecting device  10  includes a lower cushion  11  (ie., a first cushion) and an upper cushion  14  (ie., a second cushion). An exposed portion  13  is disposed in an upper surface of the lower cushion  11 . A part of an insert wire  12  is exposed in the exposed portion  13  In the upper cushion  14 , a plurality of through-holes  14   a  is disposed for inserting a suspension wire  15 . The plurality of through-holes  14   a  is overlapping with the upper surface of the lower cushion  11 . 
     From above the upper cushion  14  and the lower cushion  11 , a surface sheet  16  covers the upper cushion  14  and the lower cushion  11 . The suspension wire  15  is fixed to the surface sheet  16  and almost arranged between the surface sheet  16  and the upper cushion  14 . A flexible sensor film  18  (ie., a pressure detecting device) with fourteen through-holes  181  (ie., through-holes) which are arranged for fixing the suspension wire  15  is laid down between the upper surface of the lower cushion  11  and a lower surface of the upper cushion  14 . 
     As shown in FIG. 1, the through-holes  181  are arranged along hole lines  19  through  22 . The hole lines  19 ,  20 , and  21  are linearly located in parallel with one another in longitudinal direction relative to the sensor film  18  (ie., a top and bottom direction as viewed in FIG.  1 ), The hole line  20  is linearly located at the central portion of the sensor film  18 . The hole line  22  is located at the central portion of the sensor film  18 , and it is linearly arranged in the width direction relative to the sensor film  18 . Four through-holes  181   a ,  181   b ,  181   c , and  181   d  are arranged on the hole line  19  from an upper end to a lower end as viewed in FIG. 1 in longitudinal direction relative to the sensor film  18  with equal intervals. On the hole line  20 , four through-holes  181   e ,  181   f ,  181   g , and  181   h  are arranged from an upper end to a lower end in longitudinal direction relative to the sensor film  18  with equal intervals. On the hole line  21 , four through-holes  181   i ,  181   j ,  181   k , and  181   l  are arranged from an upper end to a lower end in longitudinal direction relative to the sensor film  18  with equal intervals. In the hole line  22 , a through-hole  181   m  is located between the hole line  19  and the hole line  20 , and a through hole  181   n  is located between the hole line  20  and the hole line  21  respectively. 
     In order to fix the surface sheet  16  in the lower cushion  11  and the upper cushion  14 , a fixing ring  17  (ie., a fixing member) is used to fix the insert wire  12  and the suspension wire  15  in the exposed portion  13  of the insert wire  12 , winding the insert wire  12  and the suspension wire  15  together. When fixing the insert wire  12  and the suspension wire  15 , the suspension wire  15  is fixed in the through-holes  14   a  and the through-holes  181 . Furthermore, when the insert wire  12  and the suspension wire are fixed through the through-holes  14   a  and the through-holes  181 , the suspension wire  15  of the surface sheet  16  is pulled in a seat. As a result, the surface sheet  16  is fixed to the upper cushion  14  and the lower cushion  11  and a design of a seat is determined when the insert wire  12  and the suspension wire  15  are fixed. 
     The surface sheet  16  is fixed in the upper cushion  14  and the lower cushion  11  by the fixing ring  17 . At the same time, the sensor film  18  is laid down and fixed between the lower surface of the upper cushion  14  and the upper surface of the lower cushion  11  by the insert wire  12  of the lower cushion  11 . 
     The upper surface of the lower cushion  11  is nearly flat, and as shown in FIG. 1, fourteen exposed portions  13  of the insert wire  12  are disposed, overlapping with the fourteen through-holes  181  of the sensor film  18 . 
     FIG. 4 is a plan view of the sensor film  18  with more details. The sensor film  18  is the FPC (ie., the flexible print circuit, in other words a print board which is inserted into a seat which is made of resin) in which a wiring portion  18   c  is connecting a plurality of a pressure sensor  18   b  is placed. A concentration portion  18   d  of the wiring portion  18   c  is connected to a control circuit of a vehicle directly or through a connector. 
     An operation of the seating detecting device  10  will be described with reference to the attached drawings. 
     When a passenger or a child seat is on a seating surface of a seat, the surface sheet  16 , the upper cushion  14 , and the lower cushion  11  are deformed because of a pressure from the object on the seating surface. 
     As shown in FIG. 4, the sensor film  18  is of a grid shape. Therefore, the sensor film  18  is deformed flexibly in accordance with a deformation of the seat. 
     As the surface sheet  16 , the upper cushion  14 , and the lower cushion  11  are deformed, the sensor film  18  is also deformed, and each of the pressure detecting sensors  18   b  receives the pressure respectively. 
     Electric current is always applied in the pressure detecting sensors  18   b , and when the pressure is applied on the pressure detecting sensor  18 , a resistance value of each pressure sensor  18   b  changes accordingly. 
     When the pressure on the seat exceeds the determined threshold value, the pressure sensor  18   b  functions to indicate the analog change of the resistance value. 
     As shown in FIG. 4, because each of the pressure sensors  18   b  is placed in lines, a gap in a amount of the pressure they receive among the adjacent pressure sensors  18   b  occurs. 
     For instance, when a passenger sits on the seat, there is a gap in the amount of the pressure between a part in which a buttock is on and a part in which the buttock is not on. Also, even within the part in which the buttock is on, the gaps among each pressure sensor  18   b  occur. Furthermore, when an object in which the pressure is put on small areas such as a foot portion of a child seat, the gaps among each pressure sensor  18   b  would be widened. 
     Because of the differences in the amount of pressure, the gap among the resistance values of each pressure sensor  18   b  occurs. The control circuit detects such gaps in the resistance values and a distribution of the pressure. As a result of the detections, the control circuit calculates and identifies a size, a shape, and a weight of the object on the seat surface of the seat. 
     Normally, a design of a seating portion of a seat is different in accordance with a type of a vehicle. The design of the seating portion is determined primarily by a layout of a suspension wire. 
     According to an embodiment of the invention, three of the layout patterns of the suspension wire  15  are shown in FIG.  3 . As above mentioned, the sensor film  18  and the lower cushion  11  of the embodiment of the invention is structured that the fourteen through-holes  181  and the exposed portions  13  of the insert wire  12  are arranged in the longitudinal direction and the lateral direction relative to the sensor film  18 . As for examples shown in FIG. 3 a  through FIG. 3 c , these layout patterns of the suspension wires  15  overlap vertically with the sensor film  18 . 
     As for FIG. 3 a , one suspension wire  15  is located in one end of the width direction relative to the sensor film  18  (ie., the lateral direction as viewed in FIG.  3 ), and another wire  15  is located in the other end of the width direction relative to the sensor film  18 , and these two suspension wires  15  are linearly arranged in parallel with one another in longitudinal direction relative to the sensor film  18 . Furthermore, one suspension wire  15  is located at the central portion of the sensor film  18 , and it is linearly arranged in the width direction relative to the sensor film  18 . The suspension wires  15  of FIG. 3 a  overlap with the hole lines  19 ,  21 , and  22  and the vertical direction of the sensor film  18 . In this pattern, among fourteen through-holes  181 , the suspension wires  15  can be inserted into four of the through-holes  181   a ,  181   b ,  181   c , and  181   d  on the hole line  19 , four of the through-holes  181   i ,  181   j ,  181   k , and  181   l  on the hole line  21 , and two of the through-holes  181   m  and  181   n  on the hole line  22  selectively. 
     As for FIG. 3 b , two suspension wires  15  are located in both ends of the width direction relative to the pressure detecting sensor  18 . In addition, one suspension wire  15  is located at the central portion of the width direction relative to the sensor film  18 . These three suspension wires  15  are linearly arranged in parallel with one another in longitudinal direction relative to the sensor film  18 . The suspension wires  15  of FIG. 3 b  overlap with the hole lines  19 ,  20 , and  21  and the vertical direction of the sensor film  18 . In this pattern, among fourteen through-holes  181 , the suspension wires  15  can be inserted into four of the through-holes  181   a ,  181   b ,  181   c , and  181   d  on the hole line  19 , four of the through-holes  181   e ,  181   f ,  181   g , and  181   h  on the hole line  20 , and four of the through-holes  181   i ,  181   j ,  181   k , and  181   l  on the hole line  21  selectively. 
     As for FIG. 3 c , two the suspension wires  15  are located in both ends of the width direction relative to the sensor film  18  respectively, and they are linearly arranged in parallel with one another in longitudinal direction relative to the film sensor  18 . Furthermore, one suspension wire  15  is located at the central portion of the sensor film  18 , and it is arranged linearly from the center of the sensor film  18  to the lower end in the longitudinal direction relative to the sensor film  18 . In addition, one suspension wire  15  is located at the central portion of the width direction relative to the sensor film  18 . This suspension wire  15  is arranged linearly in the width direction relative to the sensor film  18 . The suspension wires  15  of FIG. 3 c  overlap with the hole lines  19 ,  20 ,  21 , and  22  and the vertical direction of the sensor film  18 . In this pattern, among fourteen through-holes  181 , the suspension wires  15  can be inserted into four of the through-holes  181   a ,  181   b ,  181   c , and  181   d  on the hole line  19 , two of the through-holes  181   g  and  181   h  on the hole line  20 , four of the through-holes  181   i ,  181   j ,  181   k , and  181   l  on the hole line  21 , and two of the through-holes  181   m  and  181   n  on the hole line  22  selectively. 
     By the above structure, one layout pattern of the sensor film  18  and the lower cushion  11  shown in FIG. 1 can be applied to the surface sheet  16  which has at least three layout patterns of the suspension wire  15 . In other words, it is understood that the above sensor film  18  can be applied to a seat which is comprised of at least three types of designs of the surface sheet  16 . 
     In addition, other than placing the through-holes  181  in the longitudinal and lateral directions, the lower cushion  11  and the sensor film  18  can be applied to more various designs of seats by arranging the layout patterns of the exposed portion  13  of the insert wire  12  and the through-hole  181  in an oblique direction, or by changing the distance among each through-holes  181  and the exposed portion  13  of the insert wire  12 . 
     In the embodiment of the present invention, a plurality of analog electric signals is used as pressure detecting elements in the sensor film  18  which is used as a pressure detecting device. However, instead of analog signals, a plurality of pressure switches which outputs on/off signals can be applied. 
     A seating detecting device of this invention has an area which can cover the entire area of a seating surface of a seat, and is applicable to various designs of seats. Therefore, while the device can reduce the manufacturing cost, it can achieve in detecting an object on a seat such as a child seat with high precision. 
     The pressure detecting device according to the invention is not interfered with the suspension wire because the suspension wire of the seating detecting device is fixed through the through-holes of the pressure detecting device. Therefore, a restriction of a size of the seating detecting device to avoid the interference with the suspension wire is not necessary. Consequently, an area for the seating detecting device can be extended to the entire upper surface of the first cushion, in other words, to a whole area of the seating surface of the seat. Furthermore, with the above structure, by using the plurality of the through-holes selectively, different layout patterns of the suspension wire can be used. Therefore, the seating detecting device can be installed in plural forms of surface sheets in which the suspension wire of different layout patterns are arranged. The forms of surface sheets determine designs of seats. Thus, the pressure detecting device can be arranged in various designs of seats. 
     The plurality of through-holes are placed in flat in the above structure. By fixing the suspension wire in the predetermined through-holes of the pressure detecting device selectively, the layout patterns of the suspension wires on the surface of the seat can be various. Therefore, the pressure detecting sensor can be placed in more various designs of seats. 
     Furthermore, according to the seating detecting device of the present invention, the seating detecting device can obtain a plurality of output results from the plurality of seating detecting elements.