Patent Publication Number: US-11642983-B2

Title: Vehicle seat

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Stage entry of International Application No. PCT/JP2019/026344 filed under the Patent Cooperation Treaty having a filing date of Jul. 2, 2019, which claims priority to Japanese Patent Application No. 2018-164256 having a filing date of Sep. 3, 2018, Japanese Patent Application No. 2018-192290 having a filing date of Oct. 11, 2018, and Japanese Patent Application No. 2018-192291 having a filing date of Oct. 11, 2018, all of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a vehicle seat. 
     BACKGROUND OF THE INVENTION 
     A vehicle seat having a seat sensor installed in the seat cushion thereof is known (for example, Patent Document 1). The seat sensor is provided with a film-type pressure sensor positioned on the surface (upper surface) of the seat cushion pad. The pressure sensor is a sensor that detects the pressure applied to the seating surface of the seat cushion, and detects that a seat occupant is seated. The pressure sensor is connected to a control unit via a wire harness that is passed through a hole vertically extending through the seat cushion pad and extends to the back surface (lower surface) side of the seat cushion pad. According to this arrangement, the wire harness can be positioned so as not to contact the occupant. 
     A known seat sensor includes a plurality of pressure-sensitive switches arranged in a seating region of a vehicle seat, and configured to turn on by the seating of an occupant (for example, Patent Document 2). The seat sensor disclosed in Patent Document 2 includes a flexible sheet material, a plurality of pressure-sensitive switches provided on the sheet material, and wiring provided on the sheet material and connected to the pressure-sensitive switches. The pressure-sensitive switches are arranged so as to form a plurality of pairs arranged in the fore and aft direction, each pair containing two pressure-sensitive switches arranged laterally one next to the other and connected in series so as to form an individual sensor unit. The detection circuit becomes conductive and the seat sensor turns on when the two pressure-sensitive switches of at least one of the sensor units are both turned on. Since the sensor units are arranged in the fore and aft direction, the seat sensor is able to detect the seating of an occupant without regard if the occupant is seated on a front part of the seating region or on a rear part of the seating region. 
     PRIOR ART DOCUMENT(S) 
     Patent Document(s) 
     Patent Document 1: JP2017-65659A 
     Patent Document 1: JP2007-526844A 
     SUMMARY OF THE INVENTION 
     Task to be Accomplished by the Invention 
     However, in the case of a rear seat, since the pads constituting the seat cushion and the seat back are supported by the vehicle body panel, an adequate space cannot be secured on the back side of the pad for placing the wire harness. 
     In view of such a problem of the prior art, a primary object of the present invention to provide a vehicle seat having a pad supported by a panel which allows wire harness to be placed on the back side of the pad. 
     Means to Accomplish the Task 
     To achieve such an object, the present invention provides a vehicle seat ( 1 ), comprising: a panel ( 4 ); a pad ( 11 ,  51 ) supported by the panel; a skin material ( 12 ,  52 ) covering a front surface of the pad; and a sensor ( 32 ) provided between the front surface of the pad and the skin material for acquiring information on a seat occupant, wherein the pad is provided with a through hole ( 35 ,  58 ) passed from the front surface of the pad to a back surface of the pad, and a recess ( 45 ,  61 ) formed in the back surface of the pad and connected to the through hole, the sensor being connected to a wire harness extending in the through hole and the recess. 
     Thus, in a vehicle seat having a pad supported by a panel, the recess creates a space between the panel and the back surface of the pad so that the wire harness can be placed in this space. 
     In this invention, preferably, the recess extends from the through hole to an edge of the back surface of the pad. 
     Thereby, the wire harness positioned on the back surface of the pad can be drawn out to the side part of the pad. 
     In this invention, preferably, the surface of the panel ( 5 ) faces vertically, the pad ( 11 ) is placed on an upper surface of the panel so as to be rotatable around a center (X 1 ) located in a rear end portion thereof, and the recess extends rearward from the through hole. Alternatively, the surface of the panel ( 6 ) faces in a fore and aft direction, the pad ( 51 ) is positioned on a front surface of the panel so as to be rotatable around a center (X 2 ) located in a lower end portion thereof, and the recess extends downward from the through hole. 
     Since the wire harness extends on the back surface of the pad from the through hole toward the rotation center, the distance between an end of the wire harness and the panel changes very little when the pad rotates relative to the panel so that the wire harness is prevented from being pulled. 
     In this invention, preferably, the pad includes a plurality of members ( 14 ,  15 ) made of different materials, and the through hole is formed in one of the members. 
     Thereby, the through hole can be formed with ease. 
     In this invention, preferably, an air passage ( 37 ) extending from the back surface to the front surface is formed in the pad, and the through hole is formed so as to avoid the air passage. Preferably, a locking portion ( 41 ) for fixing a child seat is formed on the surface of the pad, and the through hole is formed so as to avoid the locking portion. Further, preferably, a heater cloth ( 43 ) having a heater wire is provided on the front surface of the pad, and the through hole is positioned so as to avoid the heater cloth. 
     Thereby, the interference of other components with the wire harness can be minimized. 
     In this invention, preferably, one end of the through hole is provided at a position avoiding a pressure receiving area ( 30 ) defined as an area on the surface of the pad to which a load of a seat occupant is directly applied. Preferably, the surface of the panel faces vertically, the pad is positioned on an upper surface of the panel, and the through hole is provided behind the pressure receiving area. 
     Thereby, the load of the occupant is prevented from being applied to the wire harness. 
     When a plurality of pressure sensors are arranged close to each other on a continuous sheet, a load applied within the detection range of a certain pressure sensor may produce a stress in the sheet so that a deformation of the sheet may be caused, and the other sensors may erroneously detect the load. In view of this fact, another object of the present invention is to prevent such an erroneous detection by the seat sensor. 
     To achieve such an object, the present invention further provides a seat sensor ( 110 ) provided between an upper surface of a seat cushion pad ( 106 ) forming a seat cushion ( 102 ) of a vehicle seat ( 101 ) and a skin material ( 107 ) covering the seat cushion pad, comprising: a flexible sheet material ( 111 ); a plurality of pressure-sensitive switches ( 112 ) provided on the sheet material; and wiring ( 113 ) provided on the sheet material and connected to the pressure-sensitive switches provided on the sheet material, wherein the sheet material includes a laterally extending main part ( 111 A) and a plurality of branch parts ( 111 B to  111 J) extending forward or rearward from the main part, the pressure-sensitive switches being provided at distal ends of the respective branch parts. 
     Since each pressure-sensitive switch is connected to the adjacent pressure-sensitive switch via the branch part, the main part, and the branch part, the deformation of any particular branch part caused by the load applied to the pressure-sensitive switch on this branch part is less likely to be transmitted to the branch part on which the adjoining pressure-sensitive switch is located. Therefore, erroneous detection by the adjacent pressure-sensitive switches can be minimized. 
     In this invention, preferably, the main part extends from a left half of the occupant&#39;s seating region ( 105 ) to a right half thereof, and the branch parts include a first branch part ( 111 B) and a second branch part ( 111 C) that are positioned in the left half of the seating region laterally spaced apart from each other, and a third branch part ( 111 D) and a fourth branch part ( 111 E) that are positioned in the right half of the seating region laterally spaced apart from each other. Further, the pressure-sensitive switches include a first pressure-sensitive switch ( 112 B) provided at a tip of the first branch part, a second pressure-sensitive switch ( 112 C) provided at a tip of the second branch part, a third pressure-sensitive switch ( 112 D) provided at a tip of the third branch part, and a fourth pressure-sensitive switch ( 112 E) provided at a tip of the fourth branch, and the first to the fourth pressure-sensitive switches are arranged on a first imaginary straight line (L 1 ) extending laterally. 
     Thus, even when the first to fourth pressure-sensitive switches are arranged close to each other along the lateral direction, erroneous detection of the pressure-sensitive switches can be minimized. 
     In this invention, preferably, the hip point (HP) of the occupant is located on the first imaginary straight line. 
     Thereby, the first to fourth pressure-sensitive switches can be arranged in an area where the load of the occupant is most likely to be applied. 
     In this invention, preferably, the wiring connects the first pressure-sensitive switch and the second pressure-sensitive switch in parallel to each other to form a first circuit ( 116 ), connects the third pressure-sensitive switch and the fourth pressure-sensitive switch in parallel to each other to form a second circuit ( 117 ), and connects the first circuit and the second circuit in series to each other. 
     The seat sensor can thereby reliably detect the occupant without regard to the difference in the stature/build of the occupant and the lateral shifting of the occupant&#39;s seating position. 
     In this invention, preferably, the first branch part and the first pressure-sensitive switch are disposed leftward of the second branch part and the second pressure-sensitive switch, and the third branch part and the third pressure-sensitive switch are arranged leftward of fourth branch and the fourth pressure-sensitive switch. Further, the first pressure-sensitive switch is configured to be turned on under a larger load than the second pressure-sensitive switch, and the fourth pressure-sensitive switch is configured to be turned on under a larger load than the third pressure-sensitive switch. 
     Thereby, the seat sensor is prevented from erroneously detecting an object other than an occupant. More specifically, the laterally outer pressure-sensitive switches, or the first and fourth pressure-sensitive switches, are configured to be turned on under a larger load to detect an occupant of a larger physical stature/build. Since the laterally outer pressure-sensitive switches are thus configured to be turned on under a larger load, these pressure-sensitive switches are prevented from being turned on by an object lighter than a seat occupant. 
     In this invention, preferably, the first to fourth branch parts extend rearward from the main part, and the branch parts further include a fifth branch part ( 111 F) and a sixth branch part ( 111 G) that extend forward in the left half of the seating region laterally spaced apart from each other, and a seventh branch part ( 111 H) and an eighth branch part ( 111 J) that extend forward in the right half of the seating region laterally spaced apart from each other, and the pressure-sensitive switches include a fifth pressure-sensitive switch ( 112 F) provided at a tip of the fifth branch part, a sixth pressure-sensitive switch ( 112 G) provided at a tip of the sixth branch part, a seventh pressure-sensitive switch ( 112 H) provided at a tip of the seventh branch part; and an eighth pressure-sensitive switch ( 112 J) provided at a tip of the eighth branch part, wherein the fifth to eighth pressure-sensitive switches are arranged on a second imaginary straight line (L 2 ) extending laterally. 
     By thus forming a rear switch row consisting of the first to fourth pressure-sensitive switches and a front switch row consisting of the fifth to eighth pressure-sensitive switches, the seat occupant can be reliably detected even when the seating position of the occupant is shifted to the front or to the rear. 
     In this invention, preferably, the wiring connects the fifth pressure-sensitive switch and the sixth pressure-sensitive switch in parallel to each other form a third circuit ( 118 ), and the seventh pressure-sensitive switch and the eighth sensor in parallel to each other to form a fourth circuit ( 119 ) while the third circuit and the fourth circuit are connected in series to each other, the first circuit and the second circuit being connected in parallel to the third circuit and the fourth circuit. 
     The front switch row including the fifth to eighth pressure-sensitive switches can reliably detect the seat occupant even when the physical stature/build of the seat occupant varies, or the occupant&#39;s seating position shifts in the lateral direction. 
     In this invention, preferably, the fifth branch part and the fifth pressure-sensitive switch are positioned leftward of the sixth branch part and the sixth pressure-sensitive switch, and the seventh branch part and the seventh pressure-sensitive switch are positioned leftward of the eighth branch part and the eighth pressure-sensitive switch. Further, the fifth pressure-sensitive switch is configured to be turned on under a larger load than the sixth pressure-sensitive switch, and the eighth pressure-sensitive switch is configured to be turned on under a larger load than the seventh pressure-sensitive switch. 
     The front switch row consisting of the fifth to eighth pressure-sensitive switches are prevented from erroneously detecting an object other than a seat occupant. 
     In this invention, preferably, the first branch part and the fifth branch part are linearly arranged in a fore and aft direction, the second branch part and the sixth branch part are linearly arranged in the fore and aft direction, the third branch part and the seventh branch part are linearly arranged in the fore and aft direction, and the fourth branch part and the eighth branch part are linearly arranged in the fore and aft direction. 
     Thereby, the shape of the sheet material can be simplified. 
     In this invention, preferably, the branch parts include a ninth branch part ( 111 K) extending forward or rearward from the main part and having a connecting portion ( 114 ) for connecting to an external wiring at a tip thereof, the connecting portion being positioned behind the second imaginary straight line and forward of the first imaginary straight line. 
     Thereby, the overall fore and aft width of the seat sensor can be minimized, and the seat sensor can be formed as a compact unit. 
     In this invention, preferably, the vehicle seat forms a rear seat of an automobile. 
     In this case, the seat sensor can correctly detect a seat occupant seating on the rear seat where the seating posture of the seat occupant can largely vary. 
     When an object is placed on the seating surface, pressure is applied to the seating surface, and the pressure is detected by the pressure sensor. Therefore, when only a pressure sensor is used, there may be some difficulty in distinguishing if a seat occupant is seated on the seating surface or an object is placed on the seating surface. Based on this recognition, a primary object of the present invention is to provide a vehicle seat that can distinguish if a seat occupant is seated on the seating surface or an object is placed on the seating surface in a more accurate manner. 
     To achieve such an object, a certain embodiment of the present invention consists of a vehicle seat ( 201 ,  251 ,  261 ,  271 ) including a seat cushion ( 204 ) and a seat back ( 205 ) provided in a rear part of the seat cushion, the vehicle seat comprising: a pressure sensor ( 20 ) provided on the seat cushion; a capacitance sensor ( 240 ,  253 ,  254 ) provided on at least one of the seat cushion and the seat back, and a determination unit ( 246 ) for determining if an occupant is seated according to a signal from the pressure sensor and a signal from the capacitance sensor. 
     If an occupant is seated or not can be determined from the signal from the pressure sensor and the signal from the capacitance sensor so that the distinction between the seating of an occupant and the placement of an object on the seating surface can be made in a more reliable manner. 
     In this invention, preferably, the capacitance sensor is provided on the seat back. 
     Thus, the pressure sensor is provided on the seat cushion, and the capacitance sensor is provided on the seat back. As a result, the pressure sensor and the capacitance sensor can be positioned so as not to interfere with each other without any difficulty, as compared with the case where both the pressure sensor and the capacitance sensor are provided on the seat cushion. Therefore, the two sensors are enabled to operate without any risk of mutual interferences. Also, as compared with the case where both the pressure sensor and the capacitance sensor are provided on the seat cushion, wiring for the pressure sensor and the capacitance sensor can be simplified. 
     In this invention, preferably, the capacitance sensor is provided at a position corresponding to a hip (H) (lumbar region) of an occupant. 
     Since the capacitance sensor is positioned so as to be close to the seated occupant, the seating of the occupant can be detected with a higher sensitivity. 
     In this invention, preferably, the seat cushion is provided with a lateral listing groove ( 215 ) extending laterally for receiving a listing strip of the skin material, and the pressure sensor includes a pair of pressure sensors, one placed ahead of the listing groove and the other placed behind the listing groove. 
     Thereby, the assembling of the pressure sensors is facilitated. Also, deformation and displacement of the pressure sensors can be avoided. Further, by placing the pressure sensors ahead of and behind the laterally extending listing groove, the pressure applied to the seating surface of the seat cushion can be detected over a wider range. 
     In this invention, preferably, the seat back is provided with a pair of longitudinal listing grooves ( 236 ) each for receiving a listing strip of the skin material, and the capacitance sensor is provided between the left and right longitudinal listing grooves. 
     Thereby, the assembling of the capacitance sensor is facilitated. Further, deformation and displacement of the capacitance sensor can be minimized. 
     In this invention, preferably, both the pressure sensor and the capacitance sensor ( 253 ,  254 ) are provided on the seat cushion. 
     Thus, the capacitance sensor is provided on the seat cushion on which the occupant sits. Therefore, the capacitance sensor is positioned close to the seating surface with which the occupant comes into contact when seated so that the occupant can be detected by the capacitance sensor with an increased sensitivity. 
     In this invention, preferably, the pressure sensor and the capacitance sensor are positioned so as to at least partly overlap with each other in top view. 
     Thereby, the area of the seating surface occupied by the pressure sensor and the capacitance sensor can be minimized so that the discomfort that may be caused to the occupant due to the presence of the pressure sensor and the capacitance sensor can be minimized. 
     In this invention, preferably, the pressure sensor is positioned on top of the capacitance sensor in such a manner that the pressure sensor is located within an outer periphery of the capacitance sensor in top view. 
     Thereby, the area of the seating surface occupied by the pressure sensor and the capacitance sensor can be minimized so that the discomfort that may be caused to the occupant due to the presence of the pressure sensor and the capacitance sensor can be minimized. 
     In this invention, preferably, the seat cushion is provided with a lateral listing groove ( 215 ) extending laterally for receiving a listing strip of the skin material, and the capacitance sensor includes a pair of capacitance sensors, one positioned ahead of the lateral listing groove, and the other positioned behind the lateral listing groove, the pressure sensor including a pair of pressure sensors, one placed on top of one of the capacitance sensors, and the other placed on top of the other capacitance sensor. 
     Since the pressure sensors and the capacitance sensors are located ahead of and behind the lateral listing groove, the pressure applied to the seating surface of the seat cushion can be detected over a wider range. Since the pressure sensors and the capacitance sensors are located so as to avoid the lateral listing groove, the assembling of the pressure sensors to the seat cushion is facilitated, and the deformation and the displacement of these sensors when an occupant is seated can be minimized. 
     In this invention, preferably, the seat cushion is provided with a lateral listing groove ( 215 ) extending laterally for receiving a listing strip of the skin material, and the pressure sensor is positioned behind the lateral listing groove, and the capacitance sensor is positioned ahead of the lateral listing groove. 
     Since the pressure sensors and the capacitance sensors are both located close to the seating surface, the seating of an occupant can be detected with a high sensitivity. Since the pressure sensors and the capacitance sensors are located so as to avoid the lateral listing groove, the assembling of the pressure sensors to the seat cushion is facilitated. Further, the deformation and the displacement of these sensors when an occupant is seated can be minimized. 
     In this invention, preferably, the capacitance sensor is provided with an opening ( 263 ,  264 ) passed vertically therethrough, and positioned on the seat cushion, and the pressure sensor is positioned inside the opening. 
     Since the pressure sensor is positioned inside the opening of the capacitance sensor, the seating surface can be made more even so that the seating comfort can be improved. 
     In this invention, preferably, the upper surface of the pressure sensor and the upper surface of the capacitance sensor are flush with each other. 
     Thereby, the seating surface becomes more even so that the seating comfort can be further improved. 
     In this invention, preferably, the seat cushion is provided with a lateral listing groove ( 215 ) extending laterally for receiving a listing strip of the skin material, and the capacitance sensor includes a pair of capacitance sensors, one positioned ahead of the lateral listing groove and the other positioned behind the lateral listing groove, the pressure sensors being positioned in the openings of the capacitance sensors, respectively. 
     Since the pressure sensors and the capacitance sensors are positioned ahead of and behind the lateral listing groove, the seating of an occupant on the seating surface can be detected over a wider range. Since the pressure sensors and the capacitance sensors are located so as to avoid the lateral listing groove, the assembling of the pressure sensors and the capacitance sensors to the seat cushion is facilitated. Since the pressure sensors are positioned inside the openings of the capacitance sensors, respectively, the seating surface can be made more even so that the seating comfort can be improved. 
     Effect of the Invention 
     According to the embodiment of the present invention which was mentioned earlier, in a vehicle seat having a pad supported by the panel, the recess creates a space between the panel and the back surface of the pad so that the wire harness can be placed in this space. 
     When the recess extends from the through hole to an edge of the back surface of the pad, the wire harness positioned on the back surface of the pad can be drawn out to the side part of the pad. 
     According to the embodiment in which the surface of the panel faces vertically, the pad is placed on an upper surface of the panel so as to be rotatable around a center located in a rear end portion thereof, and the recess extends rearward from the through hole, or alternatively, the surface of the panel faces in a fore and aft direction, the pad is disposed on a front surface of the panel so as to be rotatable around a center located in a lower end portion thereof, and the recess extends downward from the through hole, the distance between the end of the wire harness and the panel changes very little when the pad rotates relative to the panel so that the wire harness is prevented from being pulled. 
     When the pad includes a plurality of members made of different materials, and the through hole is formed in one of the members, the through hole can be formed with ease. 
     According to an embodiment in which an air passage extending from the back surface to the front surface is formed in the pad, and the through hole is formed so as to avoid the air passage, a locking portion for fixing a child seat is formed on the surface of the pad, and the through hole is formed so as to avoid the locking portion, or a heater cloth having a heater wire is provided on the front surface of the pad, and the through hole opens at a position avoiding the heater cloth, the interference of other components with the wire harness can be minimized. 
     According to an embodiment in which one end of the through hole is provided at a position avoiding a pressure receiving area defined as an area on the surface of the pad to which a load of a seat occupant is directly applied or, the surface of the panel faces vertically, the pad is positioned on the upper surface of the panel, and the through hole is provided behind the pressure receiving area, the load of the occupant is prevented from being applied to the wire harness. 
     When the sheet material includes a laterally extending main part and a plurality of branch parts extending forward or rearward from the main part, the pressure-sensitive switches being provided at distal ends of the respective branch parts, since each pressure-sensitive switch is connected to the adjacent pressure-sensitive switch via the branch part, the main part, and the branch part, the deformation of any particular branch part caused by the load applied to the pressure-sensitive switch on this branch part is less likely to be transmitted to the branch part on which the adjoining pressure-sensitive switch is located, erroneous detection by the adjacent pressure-sensitive switches can be minimized. 
     When the branch parts include a first branch part and a second branch part that are positioned in the left half of the seating region laterally spaced apart from each other, and a third branch part and a fourth branch part that are positioned in the right half of the seating region laterally spaced apart from each other, and the first to the fourth pressure-sensitive switches are arranged on a first imaginary straight line extending laterally, even when the first to fourth pressure-sensitive switches are arranged close to each other along the lateral direction, erroneous detection of the pressure-sensitive switches can be minimized. 
     When the hip point of the occupant is located on the first imaginary straight line, the first to fourth pressure-sensitive switches can be arranged in an area where the load of the occupant is most likely to be applied. 
     When the wiring connects the first pressure-sensitive switch and the second pressure-sensitive switch in parallel to each other to form a first circuit, connects the third pressure-sensitive switch and the fourth pressure-sensitive switch in parallel to each other to form a second circuit, and connects the first circuit and the second circuit in series to each other, the seat sensor can reliably detect the occupant without regard to the difference in the stature/build of the occupant and the lateral shifting of the occupant&#39;s seating position. 
     When the first pressure-sensitive switch is configured to be turned on under a larger load than the second pressure-sensitive switch, and the fourth pressure-sensitive switch is configured to be turned on under a larger load than the third pressure-sensitive switch, the seat sensor is prevented from erroneously detecting an object other than an occupant. Since the laterally outer pressure-sensitive switches are thus configured to be turned on under a larger load, these pressure-sensitive switches are prevented from being turned on by an object lighter than a seat occupant. 
     The branch parts may further include a fifth branch part and a sixth branch part that extend forward in the left half of the seating region laterally spaced apart from each other, and a seventh branch part and an eighth branch part that extend forward in the right half of the seating region laterally spaced apart from each other, and the fifth to the eighth pressure-sensitive switches may be arranged on a second imaginary straight line extending laterally. By thus forming the rear switch row consisting of the first to fourth pressure-sensitive switches and the front switch row consisting of the fifth to eighth pressure-sensitive switches, the seat occupant can be reliably detected even when the seating position of the occupant is shifted to the front or to the rear. 
     When the wiring connects the fifth pressure-sensitive switch and the sixth pressure-sensitive switch in parallel to each other to form a third circuit, and the seventh pressure-sensitive switch and the eighth sensor in parallel to each other to form a fourth circuit while the third circuit and the fourth circuit are connected in series to each other, the first circuit and the second circuit being connected in parallel to the third circuit and the fourth circuit, the front switch row including the fifth to eighth pressure-sensitive switches can reliably detect the seat occupant even when the physical stature/build of the seat occupant varies, or the occupant&#39;s seating position shifts in the lateral direction. 
     When the fifth pressure-sensitive switch is configured to be turned on under a larger load than the sixth pressure-sensitive switch, and the eighth pressure-sensitive switch is configured to be turned on under a larger load than the seventh pressure-sensitive switch, the front switch row consisting of the fifth to eighth pressure-sensitive switches are prevented from erroneously detecting an object other than a seat occupant. 
     When the first branch part and the fifth branch part are linearly arranged in a fore and aft direction, the second branch part and the sixth branch part are linearly arranged in the fore and aft direction, the third branch part and the seventh branch part are linearly arranged in the fore and aft direction, and the fourth branch part and the eighth branch part are linearly arranged in the fore and aft direction, the shape of the sheet material can be simplified. 
     When the connecting portion provided at the tip of the ninth branch part is positioned behind the second imaginary straight line and forward of the first imaginary straight line, the overall fore and aft width of the seat sensor can be minimized, and the seat sensor can be formed as a compact unit. 
     When the vehicle seat forms a rear seat of an automobile, the seat sensor can correctly detect a seat occupant seating on the rear seat where the seating posture of the seat occupant can largely vary. 
     When the vehicle seat comprises a pressure sensor provided on the seat cushion, a capacitance sensor provided on at least one of the seat cushion and the seat back, and a determination unit for determining if an occupant is seated according to a signal from the pressure sensor and a signal from the capacitance sensor, the distinction between the seating of an occupant and the placement of an object on the seating surface can be made in a more reliable manner. 
     In this embodiment, when the capacitance sensor is provided on the seat back, the pressure sensor and the capacitance sensor can be positioned so as not to interfere with each other without any difficulty, as compared with the case where both the pressure sensor and the capacitance sensor are provided on the seat cushion. Also, as compared with the case where both the pressure sensor and the capacitance sensor are provided on the seat cushion, wiring for the pressure sensor and the capacitance sensor can be simplified. 
     In this embodiment, when the capacitance sensor is provided at a position corresponding to a hip of an occupant, since the capacitance sensor is positioned so as to be close to the seated occupant, the seating of the occupant can be detected with a higher sensitivity. 
     In this embodiment, when the seat cushion is provided with a lateral listing groove extending laterally for receiving a listing strip of the skin material, and the pressure sensor includes a pair of pressure sensors, one placed ahead of the listing groove and the other placed behind the listing groove, the assembling of the pressure sensors is facilitated. Also, deformation and displacement of the pressure sensors can be avoided. Further, by placing the pressure sensors ahead of and behind the laterally extending listing groove, respectively, the pressure applied to the seating surface of the seat cushion can be detected over a wider range. 
     In this embodiment, when the seat back is provided with a pair of longitudinal listing grooves each for receiving a listing strip of the skin material, and the capacitance sensor is provided between the left and right longitudinal listing grooves, the assembling of the capacitance sensor is facilitated. Further, deformation and displacement of the capacitance sensor can be minimized. 
     In this embodiment, when both the pressure sensor and the capacitance sensor are provided on the seat cushion, the capacitance sensor is positioned close to the seating surface with which the occupant comes into contact when seated so that the occupant can be detected by the capacitance sensor with an increased sensitivity. 
     In this embodiment, when the pressure sensor and the capacitance sensor are positioned so as to at least partly overlap with each other in top view, the area of the seating surface occupied by the pressure sensor and the capacitance sensor can be minimized so that the discomfort that may be caused to the occupant due to the presence of the pressure sensor and the capacitance sensor can be minimized. 
     In this embodiment, when the pressure sensor is positioned on top of the capacitance sensor in such a manner that the pressure sensor is located within an outer periphery of the capacitance sensor in top view, the area of the seating surface occupied by the pressure sensor and the capacitance sensor can be minimized so that the discomfort that may be caused to the occupant due to the presence of the pressure sensor and the capacitance sensor can be minimized. 
     In this embodiment, when the seat cushion is provided with a lateral listing groove extending laterally for receiving a listing strip of the skin material, and the capacitance sensor includes a pair of capacitance sensors, one positioned ahead of the lateral listing groove, and the other positioned behind the lateral listing groove, the pressure sensor including a pair of pressure sensors, one placed on top of one of the capacitance sensors, and the other placed on top of the other capacitance sensor, since the pressure sensors and the capacitance sensors are located ahead of and behind the lateral listing groove, the pressure applied to the seating surface of the seat cushion can be detected over a wider range. Since the pressure sensors and the capacitance sensors are located so as to avoid the lateral listing groove, the assembling of the pressure sensors to the seat cushion is facilitated, and the deformation and the displacement of these sensors when an occupant is seated can be minimized. 
     In this embodiment, when the seat cushion is provided with a lateral listing groove extending laterally for receiving a listing strip of the skin material, and the pressure sensor is positioned behind the lateral listing groove, and the capacitance sensor is positioned ahead of the lateral listing groove, since the pressure sensor and the capacitance sensor are both located close to the seating surface, the seating of an occupant can be detected with a high sensitivity. Since the pressure sensor and the capacitance sensor are located so as to avoid the lateral listing groove, the assembling of the pressure sensors to the seat cushion is facilitated. Further, the deformation and the displacement of these sensors when an occupant is seated can be minimized. 
     In this embodiment, when the capacitance sensor is provided with an opening passed vertically therethrough, and placed in the seat cushion, and the pressure sensor is positioned inside the opening, since the pressure sensor is positioned inside the opening of the capacitance sensor, the seating surface can be made more even so that the seating comfort can be improved. 
     In this embodiment, when the upper surface of the pressure sensor and the upper surface of the capacitance sensor are flush with each other, the seating surface becomes more even so that the seating comfort can be further improved. 
     In this embodiment, when the seat cushion is provided with a lateral listing groove extending laterally for receiving a listing strip of the skin material, and the capacitance sensor includes a pair of capacitance sensors, one positioned ahead of the lateral listing groove and the other positioned behind the lateral listing groove, the pressure sensors being positioned in the openings of the capacitance sensors, respectively, since the pressure sensors and the capacitance sensors are positioned ahead of and behind the lateral listing groove, the seating of an occupant on the seating surface can be detected over a wider range. Since the pressure sensors and the capacitance sensors are located so as to avoid the lateral listing groove, the assembling of the pressure sensors and the capacitance sensors to the seat cushion is facilitated. Since the pressure sensors is positioned inside the openings of the capacitance sensors, respectively, the seating surface can be made more even so that the seating comfort can be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a seat according to a first embodiment of the present invention; 
         FIG.  2    is a sectional view of a seat cushion pad of the first embodiment; 
         FIG.  3    is an exploded perspective view of the seat cushion pad of the first embodiment; 
         FIG.  4    is a plan view of the seat cushion pad of the first embodiment; 
         FIG.  5    is a bottom view of the seat cushion pad of the first embodiment; 
         FIG.  6    is a plan view of the seat cushion pad according to a second embodiment of the present invention; 
         FIG.  7    is a plan view of rear seat according to a third embodiment of the present invention; 
         FIG.  8    is a side view of the rear seat of the third embodiment; 
         FIG.  9    is a plan view of a seat sensor provided in the rear seat of the third embodiment; 
         FIG.  10    is a circuit diagram of the seat sensor of the third embodiment 
         FIG.  11    is a perspective view of a vehicle seat according to a fourth embodiment of the present invention; 
         FIG.  12    is a side view of the vehicle seat of the fourth embodiment and an enlarged sectional view of a part thereof adjacent to a first lateral listing groove; 
         FIG.  13    is a top view of the vehicle seat of the fourth embodiment; 
         FIG.  14    is a circuit diagram of a pressure-sensitive sensor sheet of the fourth embodiment; 
         FIG.  15    is a flowchart of a determination process; 
         FIG.  16    shows top views of a vehicle sheet when an occupant is seated in (A) a rear part, (B) a front part, and (C) a right part of a seating surface, and (D) when a sack of rice is placed on the seating surface; 
         FIG.  17    is a top view of a vehicle seat according to a fifth embodiment of the present invention; 
         FIG.  18    is a top view of a vehicle seat according to a sixth embodiment of the present invention; and 
         FIG.  19    is a top view of a vehicle seat according to a seventh embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     First Embodiment 
     A vehicle seat as applied to a rear seat of an automobile according to a first embodiment of the present invention is described in the following with reference to the appended drawings. In the following description, the left and right directions are defined from the viewpoint of an occupant seated on the seat. 
     As shown in  FIG.  1   , the seat  1  is a bench seat on which three people can be seated. The seat  1  is provided with a seat cushion  2  and a seat back  3  extending upward from a rear end of the seat cushion  2 . As shown in  FIG.  2   , the seat  1  is supported by a vehicle body panel  4  which forms a vehicle body of the automobile. The vehicle body panel  4  is formed by stamp-forming steel sheet, and has a floor portion  5  having a vertically facing surface, and a wall portion  6  which extends upward from the rear edge of the floor portion  5  and has a surface facing in the fore and aft direction. The wall portion  6  separates a cabin and a luggage space from each other. The seat cushion  2  is supported on the upper surface of the floor portion  5 , and the seat back  3  is supported on the front surface of the wall portion  6 . 
     The seat cushion  2  includes a seat cushion pad  11  supported by the floor portion  5  and a skin material  12  that covers a front surface (upper surface) of the seat cushion pad  11 . As shown in  FIGS.  2  and  3   , the seat cushion pad  11  is formed by combining a plurality of members made of different materials. The seat cushion pad  11  has a rigid part  14  that forms the outer periphery of the back part (lower part) thereof, and a soft part  15  that forms the front part (upper part) thereof and the central part of the lower part thereof. The soft part  15  has a higher flexibility than the rigid part  14  and is connected to the rigid part  14 . The rigid part  14  is, for example, EPP (foamed polypropylene), and the soft part  15  is, for example, urethane foam. Due to the structure in which the soft part  15  is supported by the rigid part  14 , the shape of the seat cushion pad  11  can be maintained. In another embodiment, in order to maintain the shape of the seat cushion pad  11 , a reinforcing material such as wire is provided inside at least one of the soft part  15  and the rigid part  14 . Optionally, a frame structure may be provided for supporting the soft part  15 . 
     The seat cushion pad  11  is rotatably supported by the floor portion  5  about a rotational axis X 1  extending laterally at the rear end thereof. The seat cushion pad  11  is preferably rotatably supported by a bracket provided on the floor portion  5 . The seat cushion pad  11  can rotate about the rotational axis X 1  between a normal position where the back surface (lower surface) thereof contacts the upper surface of the floor portion  5  to allow an occupant to be seated thereon, and a tip-up position where the front part thereof is moved upward from the normal position. In the normal position, the front end of the seat cushion pad  11  may be locked to the floor portion  5 . 
     As shown in  FIGS.  3  and  4   , a listing groove  20  for receiving listing strips of the skin material  12  is formed on the surface (upper surface) of the seat cushion pad  11 . A wire for engaging hooks of the listing strips provided on the back surface of the skin material  12  is provided in each section of the listing groove  20 . Each wire is embedded in the soft part  15  and is exposed outside in the listing groove  20 . The listing groove  20  formed in a left part of the surface of the seat cushion pad  11  corresponding to the left seat includes a pair of longitudinal grooves  21  and  22  provided on either side thereof and a pair of lateral grooves  23  and  24  provided on in a front part and a rear part thereof, respectively. 
     The left and right longitudinal grooves  21  and  22  extend in the fore and aft direction in a laterally spaced relationship in parallel to each other. The spacing between the left and right longitudinal grooves  21  and  22  is preferably larger than the distance between the hip joints of a general adult male. The front ends of the left and right longitudinal grooves  21  and  22  reach the front edge of the seat cushion pad  11 . The front lateral groove  23  extends laterally at a position ahead of the hip joints of the occupant in the proper sitting position, and is connected to the left and right longitudinal grooves  21  and  22 . The front lateral groove  23  is provided at a central part of the surface of the seat cushion pad  11  with respect to the fore and aft direction. The rear lateral groove  24  extends laterally at a position behind the hip joints of the seated occupant in the proper seating position, and is connected to the left and right longitudinal grooves  21  and  22 . The rear lateral groove  24  is provided at a position of the surface of the seat cushion pad  11  in a range of 10% to 30% of the entire longitudinal length from the rear edge with respect to the fore and aft direction. 
     The surface of the seat cushion pad  11  includes a left inclined portion  26  inclining upward from the left longitudinal groove  21  toward the left end thereof, and a right inclined portion  17  inclining upward from the right longitudinal groove  22  toward the right end thereof, and a rear inclined portion  28  inclining upward from the rear lateral groove  24  toward the rear end thereof. An area on the surface of the seat cushion pad  11  to which the load of the occupant is directly applied is defined as a pressure receiving area  30 . In the present embodiment, the pressure receiving area  30  corresponds to a region surrounded by the left and right longitudinal grooves  21  and  22  and the rear lateral groove  24 . 
     As shown in  FIGS.  2  and  4   , a sensor  32  is positioned between the front surface of the seat cushion pad  11  and the skin material  12  for acquiring information on the seat occupant. The sensor  32  may include a load sensor (pressure sensor) for detecting the load of the seated person, a blood pressure sensor for detecting the blood pressure of the seated person, a pulse sensor for detecting the pulse of the seated person, a sweat sensor for detecting the sweat of the seated person, an odor sensor that detects the odor of the seated person, a body temperature sensor that detects the body temperature of the seated person, or the like. The sensor  32  is preferably formed in a film shape, and preferably extends along the front surface of the seat cushion pad  11 . 
     In the present embodiment, the sensor  32  consists of a load sensor that detects the load of the seat occupant. The sensor  32  includes a flexible film  32 A and thin film-like detection units  32 B provided on the film  32 A. The detection units  32 B may each consist of, for example, a piezoelectric element or a thin film switch in which two metal plates are placed opposite to each other with a gap therebetween, so that when a load is applied, the two metal plates bend and come into contact with each other to conduct. The film  32 A is provided along the front surface of the seat cushion pad  11 . The film  32 A extends from the pressure receiving area  30  to the rear inclined portion  28 , and passes over the lateral groove  24  on the rear side. The skin material  12  is pulled into the rear lateral groove  24  on either lateral side of the film  32 A in order to avoid interference with the film  32 A. The front end of the film  32 A is branched and extends to in both the leftward and rightward directions. The detection units  32 B are provided at the left and right ends of the front end of the film  32 A, respectively, and are positioned in the pressure receiving area  30 . The film  32 A is provided with signal lines extending from the detection units  32 B. The film  32 A may be a flexible printed circuit board or the like. A wire harness  33  for transmitting the detection signal from the detection units  32 B is connected to a rear end part of the film  32 A of the sensor  32 . 
     A harness passage  35  is formed in the seat cushion pad  11  as a through hole passed therethrough from the front surface to the back surface. The wire harness  33  connected to the sensor  32  extends from the front side of the seat cushion pad  11  to the back side of the seat cushion pad  11  through the wire harness passage  35 . The open end of the wire harness passage  35  on the front surface side is provided at a position avoiding the pressure receiving area  30 . In the present embodiment, the open end of the wire harness passage  35  on the front surface side is provided in the rear inclined portion  28 . The wire harness passage  35  may be formed only in the soft part  15 , or may be formed in the soft part  15  and the rigid part  14 . By forming the wire harness passage  35  only in the soft part  15  while avoiding the rigid part  14 , the forming process for the wire harness passage  35  is facilitated. In the present embodiment, the wire harness passage  35  extends vertically and is passed through both the soft part  15  and the rigid part  14  so that the open end on the back surface side is formed in the rigid part  14 . The diameter of the part  35 A of the wire harness passage  35  formed in the rigid part  14  is larger than the diameter of the part  35 B of the wire harness passage  35  formed in the soft part  15 . Thus, the wire harness passage  35  consists of a stepped hole in which the diameter of the part  35 A of the wire harness passage  35  on the back surface side is increased stepwise with respect to the part  35 B of the wire harness passage  35  on the front surface side. In another embodiment, the wire harness passage  35  may extend obliquely with respect to the vertical direction. By causing the wire harness passage  35  to extend obliquely, the wire harness passage  35  can be formed only in the soft part  15  while avoiding the rigid part  14 . 
     An air passages  37  extends in the seat cushion pad  11  from the bottom surface thereof to the upper surface thereof. The air passage  37  includes a collecting portion  37 A opening on the bottom surface of the seat cushion pad  11 , and a branch part  37 B branched from the collecting portion  37 A and opening  37 C on the upper surface. A blower  38  is provided at the open end  37 D of the collecting portion  37 A. A ventilation groove  39  is formed in the floor portion  5  of the vehicle body panel  4  at a position corresponding to the open end of the collecting portion  37 A. The ventilation groove  39  extends in the fore and aft direction, and communicates with the open end of the collecting portion  37 A at the rear end thereof, and communicates with the internal space of the cabin at the front end thereof. The skin material  12  has air permeability. As the blower  38  rotates, the air drawn from the passenger compartment flows through the ventilation groove  39 , the collecting portion  37 A, and the branch part  37 B in that order, and passes through the skin material  12 . The air is then discharged upward from the seat cushion  2 . The wire harness passage  35  is formed so as to avoid the air passage  37 . In another embodiment, the wire harness passage  35  at least partly overlaps with the air passage  37 . The ventilation groove  39  may be formed on the bottom surface of the seat cushion pad  11  by suitably recessing the corresponding part thereof, instead of the floor portion  5 . 
     A rear end part of the front surface of the seat cushion pad  11  is provided with a pair of locking portions  41  for securing child seats laterally one next to the other. Each locking portion  41  includes a groove formed in the seat cushion pad  11  and a striker placed inside the groove. The locking portions  41  may be configured to comply with the international standard ISO-FIX. The wire harness passage  35  is formed so as to avoid the respective locking portions  41 . 
     As shown in  FIGS.  2  and  5   , the back surface of the seat cushion pad  11  is provided with a recess  45  connected to the open end of the wire harness passage  35  on the back surface side of the seat cushion pad  11 . The recess  45  and the floor portion  5  of the vehicle body panel  4  jointly form a space for receiving the wire harness  33  therein. The recess  45  has a groove shape and extends rearward from the wire harness passage  35 . More specifically, the recess  45  extends from the wire harness passage  35  toward the side of the rotational axis X 1  of the seat cushion pad  11 . The rear end of the recess  45  may reach the rear edge of the seat cushion pad  11 . The recess  45  may be dimensioned so as to receive an electronic component such as a connector of the wire harness  33  or a microcomputer to which the wire harness  33  is connected. 
     The wire harness  33  extends rearward from the sensor  32  provided on the front surface of the seat cushion pad  11  along the front surface of the seat cushion pad  11 , reaches the back side of the seat cushion pad  11  via the wire harness passage  35 , and then extends to the rear edge of the seat cushion pad  11  via the recess  45 . 
     As shown in  FIG.  2   , the seat back  3  includes a seat back pad  51  supported by the wall portion  6  of the vehicle body panel  4 , and a skin material  52  covering a surface (front surface) of the seat back pad  51 . The seat back pad  51  has a rigid part  53  and a soft part  54 , similarly to the seat cushion pad  11 . 
     The seat back pad  51  is rotatably supported at the lower end thereof by the wall portion  6  about a rotational axis X 2  extending laterally. The seat back pad  51  may be supported by a bracket provided on the wall portion  6  so as to be rotatable around the rotational axis X 2 . The seat back pad  51  rotates about the rotational axis X 2  between a normal position in which the back surface (rear surface) is in contact with the front surface of the wall portion  6 , and a forward tilt position in which the upper portion of the seat back pad  51  is positioned forward with respect to the normal position. In the normal position, the upper end of the seat back pad  51  is preferably locked to the wall portion  6 . In another embodiment, the seat back pad  51  is rotatably supported by the seat cushion pad  11  instead of the wall portion  6 . 
     A listing groove is formed on the surface of the seat back pad  51 , similarly to the seat cushion pad  11 . A sensor  57  is placed between the front surface of the seat back pad  51  and the skin material  52  for acquiring information on the occupant. The sensor  57  may be similar to the sensor  32  provided on the seat cushion pad  11 . 
     A harness passage  58  penetrates the seat back pad  51  from the front surface to the back surface. A wire harness  59  connected to the sensor  57  extends from the front side of the seat back pad  51  to the back side of the seat cushion pad  11  through the wire harness passage  58 . The wire harness passage  58  can be positioned similarly to the wire harness passage  35  of the seat cushion pad  11 . 
     On the back surface of the seat back pad  51  is formed a recess  61  communicating with the open end on the back surface side of the wire harness passage  58 . A space is defined between the recess  61  and the wall portion  6  of the vehicle body panel  4  to receive the wire harness  59  therein. The recess  61  has a groove shape and extends downward from the wire harness passage  58 . More specifically, the recess  61  extends from the wire harness passage  58  toward the rotational axis X 2  of the seat back pad  51 . The lower end of the recess  61  may reach the lower edge of the seat back pad  51 . 
     The effect of the seat  1  according to the foregoing embodiment is discussed in the following. Owing to the recess  45  provided on the back surface of the seat cushion pad  11 , a space is created between the floor portion  5  of the vehicle body panel  4  and the back surface of the seat cushion pad  11  so that the wire harness  33  can be positioned in this space. Similarly, a space is created between the wall portion  6  of the vehicle body panel  4  and the back surface of the seat back pad  51  by the recess  61  provided on the back surface of the seat back pad  51  so that the wire harness  59  can be positioned in this space. 
     Since the recess  45  of the seat cushion pad  11  extends rearward from the wire harness passage  35 , or in other words, toward the rotational axis X 1  of the seat cushion pad  11 , when the seat cushion pad  11  is rotated relative to the floor portion  5 , the distance between the floor portion  5  and the wire harness  33  does not change to any significant extent so that the wire harness  33  is prevented from being pulled excessively. Similarly, the recess  61  of the seat back pad  51  extends downward from the wire harness passage  58 , or in other words, toward the rotational axis X 2  of the seat back pad  51  so that the wire harness  59  is prevented from being pulled excessively. 
     Since the wire harness passage  35  opens at a position (the rear inclined portion  28 ) on the front surface of the seat cushion pad  11  that avoids the pressure receiving area  30 , the load of the occupant is prevented from being applied to the wire harness  33 . The same is true with the seat back  3 . 
     Second Embodiment 
     A seat  70  according to a second embodiment of the present invention is described in the following. As shown in  FIG.  6   , the seat  70  of the second embodiment is different from the seat  1  of the first embodiment in that the seat  70  does not have the air passage  37 , and has a heater cloth  72 . The seat  70  of the second embodiment is otherwise similar to the seat  1  of the first embodiment. Therefore, in the following disclosure, the parts having similar structures are denoted with like numerals without necessarily repeating the description of such parts. 
     The heater cloth  72  incorporated with a heater wire  73  is placed between the front surface of the seat cushion pad  11  and the skin material  12 . The heater cloth  72  has a substantially rectangular main body  72 A positioned in the pressure receiving area  30 , and a pair of connecting portions  72 B extending rearward from the rear edge of the main body  72 A along either side of the main body  72 A. The heater cloth  72  extends into the lateral grooves  23  and  24  and is passed under the skin material  12 . The connecting portions  72 B extend from the front side to the back side of the seat cushion pad  11  along the rear end of the seat cushion pad  11 . 
     The main body  72 A of the heater cloth  72  is positioned so as to overlap with the detection units  32 B of the sensor  32  and a front part of the film  32 A. Meanwhile, the open end of the wire harness passage  35  on the front side is positioned so as to avoid the heater cloth  72 . The open end of the wire harness passage  35  on the front surface side is positioned in a region defined by the rear edge of the main body  72 A and the left and right connecting portions  72 B. 
     Third Embodiment 
     A seat sensor of a vehicle seat as applied to a seat sensor for a second row or third row rear seat according to a third embodiment of the present invention is described in the following. 
     As shown in  FIG.  7   , the seat  101  includes a seat cushion  102  provided on a floor of an automobile, a pair of seat backs  103  supported on a rear portion of the seat cushion  102  laterally one next to the other, and a pair of headrests  104  provided on the upper parts of the respective seat backs  103 . The seat cushion  102  extends laterally so as to form a pair of seating regions  105  for seating a pair of occupants 
     As shown in  FIG.  8   , the seat cushion  102  includes a seat cushion pad  106  and a skin material  107  that covers the front surface of the seat cushion pad  106 . The seat cushion pad  106  may be directly supported on a floor panel of an automobile, or may be supported on a frame structure supported on the floor panel. In the present embodiment, a sheet-like wadding material  108  is provided between the skin material  107  and the seat cushion pad  106 . The wadding material  108  is optional, and may be omitted. 
     As shown in  FIG.  8   , the upper surface of each seating region  105  of the seat cushion  102  is inclined downward toward the rear end thereof. Each seating region  105  supports an occupant&#39;s buttocks and thighs. 
     As shown in  FIGS.  7  and  9   , each seating region  105  is provided with a seat sensor  110  for detecting an occupant&#39;s seating. The seat sensor  110  essentially consists of a switch that is turned on when an occupant is seated and cut off when no occupant is seated. The seat sensor  110  includes a flexible sheet material  111 , a plurality of pressure-sensitive switches  112  provided on the sheet material  111 , and wiring  113  provided on the sheet material  111  and connected to the pressure-sensitive switches. 
     The sheet material  111  is placed between the wadding material  108  and the seat cushion pad  106 . The sheet material  111  may be, for example, a flexible printed circuit board. The sheet material  111  includes a main part  111 A extending laterally, and a plurality of branch parts  111 B to  111 J extending forward or rearward from the main part  111 A. The main part  111 A extends linearly from the left half to the right half of the occupant&#39;s seating region  105 . The laterally central part of the main part  111 A coincides with a line extending in the fore and aft direction in a laterally central part of the seating region  105 . 
     In the present embodiment, the branch parts  111 B to  111 J include a first branch part  111 B, a second branch part  111 C, a third branch part  111 D, and a fourth branch part  111 E extending rearward from the main part  111 A. The branch parts  111 B to  111 J further include a fifth branch part  111 F, a sixth branch part  111 G, a seventh branch part  111 H, and an eighth branch part  111 J extending forward from the main part  111 A. In the present embodiment, the first to eighth branch parts  111 B to  111 J are orthogonal to the main part  111 A. 
     The first branch part  111 B, the second branch part  111 C, the third branch part  111 D, and the fourth branch part  111 E are arranged laterally from left to right in that order in a mutually spaced apart relationship. The first branch part  111 B and the second branch part  111 C are positioned in the left half of the seating region  105 , and the third branch part  111 D and the fourth branch part  111 E are positioned in the right half of the seating region. The lateral distance between the first branch part  111 B and the second branch part  111 C is equal to the lateral distance between the third branch part  111 D and the fourth branch part  111 E. The lateral distance between the second branch part  111 C and the third branch part  111 D is larger than the distance between the lateral distance between the first branch part  111 B and the second branch part  111 C. The lateral distance between the second branch part  111 C and the third branch part  111 D is preferably larger than the distance between the first and second branch parts  111 B and  111 C by the factor of two to three. 
     The fifth branch part  111 F, the sixth branch part  111 G, the seventh branch part  111 H, and the eighth branch part  111 J are arranged laterally from left to right in that order in a mutually spaced apart relationship. The fifth branch part  111 F and the sixth branch part  111 G are arranged on the left half of the seating region  105 , and the seventh branch part  111 H and the eighth branch part  111 J are arranged on the right half of the seating region. The fifth branch part  111 F is linearly arranged in front of the first branch part  111 B, the sixth branch part  111 G is linearly arranged in front of the second branch part  111 C, the seventh branch part  111 H is linearly arranged in front of the third branch part  111 D, and the eighth branch part  111 J is linearly arranged in front of the fourth branch part  111 E. The lateral distance between the fifth branch part  111 F and the sixth branch part  111 G and the lateral distance between the seventh branch part  111 H and the eighth branch part  111 J are each equal to the lateral distance between the first branch part  111 B and the second branch part  111 C. The lateral distance between the sixth branch part  111 G and the seventh branch part  111 H is equal to the distance between the second branch part  111 C and the third branch part  111 D. 
     The first to fourth branch parts  111 B to  111 E have the same length. The fifth to eighth branch parts  111 F to  111 J have the same length. The first to eighth branch parts  111 B to  111 J may all have an equal length. 
     A ninth branch part  111 K extends forward from a laterally central part of the main part  111 A. The front end of the ninth branch part  111 K is provided with a connecting portion  114  for connection to a wire harness  121  to provide as an external wiring. The ninth branch part  111 K is preferably shorter than the fifth to eighth branch parts  111 F to  111 J. 
     In the present embodiment, the pressure-sensitive switches  112  include first to eighth pressure-sensitive switches  112 B to  112 J. Each pressure-sensitive switch  112  is a membrane switch, and is provided on a frame-like spacer sheet, a pair of contact sheets stacked one over the other via the frame-like spacer sheet, and a pair of electric contacts provided on opposing surfaces of the contact sheets, respectively. When the pressure-sensitive switch  112  receives an external load, the contact sheets bend with the result that the two contacts come into contact with each other to be in a conductive state or the pressure-sensitive switch  112  is turned on. The pressure at which the contacts come into contact with each other can be changed by adjusting the size and thickness of the contacts, the thickness and shape of the spacer, the stiffness of the contact sheets, and the like. The pressure-sensitive switches  112  may also be of any other configuration as long as it is a switch that conducts electricity upon detecting pressure. 
     As shown in  FIG.  9   , the first pressure-sensitive switch  112 B is provided at the tip end (rear end) of the first branch part  111 B, the second pressure-sensitive switch  112 C is provided at the tip end (rear end) of the second branch part  111 C, the third pressure-sensitive switch  112 D is provided at the tip end (rear end) of the third branch part  111 D, the fourth pressure-sensitive switch  112 E is provided at the tip end (rear end) of the fourth branch part  111 E, the fifth pressure-sensitive switch  112 F is provided at the tip (tip end) of the fifth branch part  111 F, the sixth pressure-sensitive switch  112 G is provided at the tip (tip end) of the sixth branch part  111 G, the seventh pressure-sensitive switch  112 H is provided at the tip (tip end) of the seventh branch part  111 H, and the eighth pressure-sensitive switch  112 J is provided at the tip (tip end) of the eighth branch part  111 J. 
     The first to fourth pressure-sensitive switches  112 B to  112 E are arranged on a first imaginary straight line L 1  extending laterally. The fifth to eighth pressure-sensitive switches  112 F to  112 J are arranged on a second imaginary straight line L 2  extending also extending laterally. The first imaginary straight line L 1 , the second imaginary straight line L 2 , and the main part  111 A are arranged in parallel with each other. The first imaginary straight line L 1  is positioned behind the main part  111 A, and the second imaginary straight line L 2  is positioned ahead of the main part  111 A. 
     The occupant&#39;s hip point HP is positioned on the first imaginary straight line L 1 . The hip point HP is defined by the American SAE standard J-826, and is given by the rotational center points (the position of the hip joints) between the torso and the thighs of a three-dimensional mannequin. In plan view, the hip point is a central point of a line segment connecting the two rotational center points. 
     Preferably, the front edge of the connecting portion  114  provided at the tip end of the ninth branch part  111 K is positioned behind the second imaginary straight line L 2  and forward of the first imaginary straight line L 1 . Thereby, the overall fore and aft width of the seat sensor  110  can be reduced. 
     As shown in  FIG.  10   , the wiring  113  provided on the sheet material  111  connects the first to eighth pressure-sensitive switches  112 B to  112 J so as to form a detection circuit  115 . The wiring  113  connects the first pressure-sensitive switch  112 B and the second pressure-sensitive switch  112 C in parallel to each other to form a first circuit  116 , connects the third pressure-sensitive switch  112 D and the fourth pressure-sensitive switch  112 E in parallel to each other so as to form a second circuit  117 , and connects the first circuit  116  and the second circuit  117  in series to each other. Further, the wiring  113  connects the fifth pressure-sensitive switch  112 F and the sixth pressure-sensitive switch  112 G in parallel to each other to form a third circuit  118 , connects the seventh pressure-sensitive switch  112 H and the eighth pressure-sensitive switch  112 J in parallel to each other to form a fourth circuit  119 , and connects the third circuit  118  and the fourth circuit  119  in series to each other. The detection circuit  115  is formed by connecting the first circuit  116  and the second circuit  117  and the third circuit  118  and the fourth circuit  119  in parallel to one another via the wiring  113 . The two ends of the wiring  113  are provided at the connecting portion  114 , and are connected to a control unit  122  via a wire harness  121 . The wire harness  121  is passed through a passage  123  vertically penetrating the seat cushion pad  106 , and extend under the seat cushion pad  106 . The upper end of the passage  123  may be positioned on the second imaginary straight line L 2  or behind the second imaginary straight line L 2 . Thereby, the passage  123  can be formed close to the seat sensor  110  so that the area on the upper surface of the seat cushion pad  106  occupied by the wire harness  121  can be minimized. Further, the seat sensor  110  and the passage  123  can be arranged compactly. 
     The first pressure-sensitive switch  112 B is configured to be turned on under a larger load than the second pressure-sensitive switch  112 C, and the fourth pressure-sensitive switch  112 E is configured to be turned on under a larger load than the third pressure-sensitive switch  112 D. Preferably, the first pressure-sensitive switch  112 B and the fourth pressure-sensitive switch  112 E have a same ON load, and the second pressure-sensitive switch  112 C and the third pressure-sensitive switch  112 D have a same ON load. The fifth pressure-sensitive switch  112 F is configured to be turned on at a larger load than the sixth pressure-sensitive switch  112 G, and the eighth pressure-sensitive switch  112 J is configured to be turned on under a larger load than the seventh pressure-sensitive switch  112 H. The fifth pressure-sensitive switch  112 F and the eighth pressure-sensitive switch  112 J may have a same ON load, and the sixth pressure-sensitive switch  112 G and the seventh pressure-sensitive switch  112 H may have a same ON load. Preferably, the first pressure-sensitive switch  112 B and the fifth pressure-sensitive switch  112 F have a same ON load, and the second pressure-sensitive switch  112 C and the sixth pressure-sensitive switch  112 G have a same ON load. 
     An example of positioning of the pressure-sensitive switches  112  is given in the following. The lateral distance between the second pressure-sensitive switch  112 C and the third pressure-sensitive switch  112 D is preferably between 60 mm and 100 mm. The distance between the first pressure-sensitive switch  112 B and the second pressure-sensitive switch  112 C and the distance between the third pressure-sensitive switch  112 D and the fourth pressure-sensitive switch  112 E are preferably between 30 and 50 mm. The distance between the first pressure-sensitive switch  112 B and the fifth pressure-sensitive switch  112 F in the fore and aft direction is preferably between 60 mm and 80 mm. These numerical ranges include the boundary values. 
     The control unit  122  determines if the occupant is seated according to the conductive state (ON, OFF) of the seat sensor  110 . Further, the control unit  122  determines if a seat belt is worn in each seating region  105 . When the control unit  122  has determined that the occupant is seated in the seating region  105 , and the seat belt is not worn, the occupant is warned by sound or by turning on an alarm lamp. 
     The effect of the seat sensor  110  of the present embodiment is discussed in the following. The sheet material  111  includes the main part  111 A extending laterally, and the first to eighth branch part  111 B to  111 J extending forward or rearward from the main part  111 A. The first to eighth pressure-sensitive switch  112 B to  112 J are provided at the tips of the first to eighth branch parts  111 B to  111 J, respectively. Therefore, each adjacent pair of pressure-sensitive switches  112 B to  112 J are connected to each other via the two corresponding branch parts  111 B to  111 J and the main part  111 A. Therefore, when a load is applied to a certain pressure-sensitive switch  112 B- 112 J, the deformation of the branch part  111 B- 111 J on which the pressure-sensitive switch  112 B- 112 J is located is not likely to be transmitted to the branch part  111 B to  111 J on which the adjacent pressure-sensitive switch  112 B- 112 J is located. In particular, when the pressure-sensitive switches  112  are linearly arranged laterally as is the case with the first to fourth pressure-sensitive switches  112 B to  112 E or the fifth to eighth pressure-sensitive switches  112 F to  112 J, erroneous detection of the pressure-sensitive switches  112 B to  112 J due to the deformation of the sheet material  111  can be minimized. 
     Since the occupant&#39;s hip point HP is located on the first imaginary straight line L 1 , the first to fourth pressure-sensitive switches  112 B to  112 E are thus positioned at parts where the occupant&#39;s load is most likely to be applied. 
     When at least one of the first pressure-sensitive switch  112 B and the second pressure-sensitive switch  112 C is turned on and at least one of the third pressure-sensitive switch  112 D and the fourth pressure-sensitive switch  112 E is turned on, the detection circuit  115  is turned on so that the seating sensor  110  detects the seating of a seat occupant. Therefore, even when the occupant&#39;s stature/build varies or the occupant&#39;s seating position is shifted to the left or to the right, the seat sensor  110  can reliably detect the occupant. For example, when the occupant is person of a large stature/build, all of the first to fourth pressure-sensitive switches  112 B to  112 E are turned on so that the detection circuit  115  is turned on. When the occupant is small like a child, the second and third pressure-sensitive switches  112 C and  112 D are turned on so that the detection circuit  115  is turned on. When the occupant is seated with a shift to the left, at least one of the first and second pressure-sensitive switches  112 B and  112 C, and the third pressure-sensitive switch  112 D are turned on so that the detection circuit  115  is turned on. When the occupant is seated with a shift to the right, at least one of the third and fourth pressure-sensitive switches  112 D and  112 E and the second pressure-sensitive switch  112 C are turned on so that the detection circuit  115  is turned on. 
     Further, since the front switch row including the fifth to eighth pressure-sensitive switches  112 F to  112 J are provided in front of the rear switch row including the first to fourth pressure-sensitive switches  112 B to  112 E, even when the occupant is seated with a forward shift, the seat sensor  110  can reliably detect the occupant by the front switch row. 
     Since the first pressure-sensitive switch  112 B is configured to be turned on under a load greater than the second pressure-sensitive switch  112 C, and the fourth pressure-sensitive switch  112 E is configured to be turned on under a load greater than the third pressure-sensitive switch  112 D, the sensor  110  is prevented from erroneously detecting an object other than a person as an occupant. When the occupant is seated with a lateral shift, the load applied to the pressure-sensitive switch  112  located on the side of the shifted direction (the first pressure-sensitive switch  112 B when the occupant is seated with a leftward shift) becomes larger than the load applied to the pressure-sensitive switch  112 C,  112 D located on the side away from the shifted direction. When the occupant has a large stature/build, the load applied to the laterally outer pressure-sensitive switches  112 B and  112 E increases. When the stature/build of the occupant is small, the load applied to the laterally inner pressure-sensitive switches  112 C and  112 D increases. Therefore, a seat occupant can be detected in an appropriate manner if the load under which the first and fourth pressure-sensitive switches  112 B and  112 E that are located on the laterally outer sides are turned on is greater than the load under which the second and third pressure-sensitive switches  112 C and  112 D that are located on the laterally inner sides are turned on. By making the load under which the first and fourth pressure-sensitive switches  112 B and  112 E that located on the laterally outer sides are turned on to be greater than the load under which the second and third pressure-sensitive switches  112 C and  112 D located on the laterally inner sides are turned on, the first and fourth pressure-sensitive switches  112 B and  112 E are prevented from erroneously turning on under a load of an object lighter than a person. The same applies to the fifth to eighth pressure-sensitive switches  112 F to  112 J located on the front side. 
     Fourth Embodiment 
     As shown in  FIG.  11   , a pair of vehicle seats  201  according to a fourth embodiment of the present invention are arranged in the vehicle width direction or laterally one next to the other on a floor  203  that defines a bottom portion of a cabin  202  of an automobile. The two vehicle seats  201  are generally symmetrical to each other. The vehicle seats  201  form the rear seats of the second or any subsequent row in the vehicle. Each vehicle seat  201  includes a seat cushion  204  that supports the buttocks of a seated person, a seat back  205  provided at the rear end of the seat cushion  204  to function as a backrest, and a headrest  206  provided in an upper part of the seat back  205 . 
     The seat cushions  204  has a substantially rectangular parallelepiped shape having a surface that faces substantially vertically. The upper surface of the seat cushion  204  forms a seating surface  207  for a single occupant. The seating surface  207  is recessed downward in a laterally central part thereof, and is slightly inclined downward in the fore and aft direction toward the rear end thereof. Thus, the seating surface  207  has a shape corresponding to the buttocks and thighs of a seat occupant. When a occupant is seated, the buttocks and thighs of the occupant are positioned on the seating surface  207 . 
     The seat back  205  extends vertically and has a substantially rectangular parallelepiped shape having a surface that faces substantially in the fore and aft direction. The front surface of the seat back  205  forms a support surface  208  for supporting the occupant&#39;s back. The support surface  208  is recessed rearward substantially at a laterally central part thereof, and is inclined slightly rearward toward the upper end thereof. Thus, the support surface  208  has a shape corresponding to the back of the occupant, and the back of the occupant is supported by the support surface  208 . 
     The lower end of the seat back  205  is pivotally supported by the rear end of the seat cushion  204  via a per se known reclining mechanism. In other words, the seat back  205  is connected to the rear end of the seat cushion  204  at the lower end so as to be pivotable forward and backward. 
     As shown in  FIG.  12   , the seat cushion  204  includes a seat cushion frame (not shown) serving as a structural framework, a pad member  211  supported by the seat cushion frame, and a skin material  212  placed on the front surface of the pad member  211  to define the outer profile of the seat cushion  204 . 
     As shown in  FIG.  11   , the upper surface of the pad member  211  of the seat cushion  204  includes an intermediate portion  213  which is inclined downward toward the rear end thereof in a laterally middle part thereof, and a pair of bulging portions  214  bulging upward on either lateral side of the intermediate portion  213 . As shown in  FIG.  13   , the upper surface of the pad member  211  of the seat cushion  204  is further provided with a first lateral listing groove  215  extending laterally at a substantially middle part with respect to the fore and aft direction, and a pair of first longitudinal listing grooves  216  extending from the front edge and the rear edge of the seat cushion  204 . Each first longitudinal listing groove  216  is formed substantially along the boundary between the intermediate portion  213  and the corresponding bulging portion  214 . The first lateral listing groove  215  is connected to the first longitudinal listing grooves  216  at the respective ends thereof. 
     The first lateral listing groove  215  and the first longitudinal listing grooves  216  each consist of a downwardly recessed groove formed on the upper surface of the pad member  211  (refer to  FIG.  12    for the first lateral listing groove  215 ). The skin material  212  covering the pad member  211  is provided with a plurality of hook members  217  at positions corresponding to the first lateral listing groove  215  and the first longitudinal listing grooves  216 . Each hook member  217  is inserted into the first lateral listing groove  215  or the first longitudinal listing groove  216 . A fixing member  218  is provided inside each of the first lateral listing groove  215  and the first longitudinal listing grooves  216 . The hook members  217  are hooked onto the corresponding fixing members  218  so that the skin material  212  is pulled into in the first lateral listing groove  215  and the first longitudinal listing grooves  216  via corresponding listing strips. Therefore, the first lateral listing groove  215  and the first longitudinal listing grooves  216  can be considered as grooves provided in the seat cushion  204  for pulling the skin material  212  into the seat cushion  204 . 
     As shown in  FIG.  12   , a pressure-sensitive sensor unit  219  for detecting a load applied to the seating surface  207  is provided between the front surface of the pad member  211  of the seat cushion  204  and the back surface of the skin material  212  of the seat cushion  204 . The pressure-sensitive sensor unit  219  consists of a flexible sheet-like member incorporated with a plurality of pressure-sensitive switches  220  (see  FIG.  11   ), and thus forms a so-called membrane switch. Each pressure-sensitive switch  220  is provided with an electrode placed along the surface of the pressure-sensitive sensor unit  219 . Each pressure-sensitive switch is turned on (or conducts) when a load equal to or greater than a predetermined value is applied to the electrode by pressing the surface of the pressure-sensitive sensor unit  219 . Therefore, the pressure-sensitive switches  220  function as pressure sensors that detect the pressure applied to the electrodes. The pressure sensor unit  219  includes a first subunit  221  and a second subunit  222 . Each of the first subunit  221  and the second subunit  222  consists of a sheet-like member, and is incorporated with a plurality of pressure-sensitive switches  220 . As shown in  FIG.  12   , the first subunit  221  and the second subunit  222  are arranged so as to extend in the lateral direction along the surface of the pad member  211 . The back side of the first subunit  221  and the back side of the second subunit  222  are in contact with the front surface of the pad member  211  of the seat cushion  204 . The first subunit  221  and the second subunit  222  are connected to each other by wiring  223 . 
     As shown in  FIG.  13   , the first subunit  221  is positioned in front of the first lateral listing groove  215  and between the left and right first longitudinal listing grooves  216 . The second subunit  222  is located behind the first lateral listing groove  215  and between the left and right first longitudinal listing grooves  216 . Thus, the pressure-sensitive switches  220  are provided both ahead of and behind the first lateral listing groove  215 . 
     In the present embodiment, the first subunit  221  and the second subunit  222  are each provided with two pairs of pressure-sensitive switches  220 , each pair consisting of two pressure-sensitive switches  220  positioned laterally next to each other. The pressure-sensitive switch pairs are positioned at the left and right ends of the first subunit  221 , respectively, and the pressure-sensitive switch pairs are positioned at the left and right ends of the second subunit  222 , respectively. More specifically, one of the pressure-sensitive switch pairs (the first left pressure-sensitive switch pair  225 L) are provided at the left end of the first subunit  221 , and the other pressure-sensitive switch pair (the first right pressure-sensitive switch pair  225 R) are provided at the right end of the first subunit  221 . Similarly, one of the pressure-sensitive switch pairs (the second left pressure-sensitive switch pair  226 L) are provided at the left end of the second subunit  222 , and the other pressure-sensitive switch pair (the second right pressure-sensitive switch pair  226 R) are provided at the right end of the second subunit  222 . Further, the first left pressure-sensitive switch pair  225 L and the first right pressure-sensitive switch pair  225 R laterally align with each other (coincide with each other with respect to the fore and aft positioning), and the second left pressure-sensitive switch pair  226 L the second right pressure-sensitive switch pair  226 R laterally align with each other (coincide with each other with respect to the fore and aft positioning). 
       FIG.  14    shows a circuit diagram of the pressure-sensitive sensor unit  219 . As shown in  FIG.  14   , the pressure-sensitive switches  220  included in each pressure-sensitive switch pair  225 L,  225 R,  226 L and  226 R are connected in parallel to each other (two-dot chain lines in  FIG.  14   ). In other words, each pressure-sensitive switch pair  225 L,  225 R,  226 L and  226 R is turned on when either one of the corresponding pressure-sensitive switches  220  is turned on. Further, when the first left pressure-sensitive switch pair  225 L or the second left pressure-sensitive switch pair  226 L is ON and the first right pressure-sensitive switch pair  225 R or the second right pressure-sensitive switch pair  226 R is turned ON, the sensor unit  219  turns ON and becomes conductive. 
     As shown in  FIG.  12   , the seat back  205  is provided with a seat back frame (not shown) serving as a structural framework, a pad member  231  supported by the seat back frame, and a skin material  232  placed on the surface of the pad member  231  to define the outer profile of the seat back  205 . 
     As shown in  FIG.  11   , the front surface of the pad member  231  of the seat back  205  includes an intermediate portion  233  that is located substantially laterally central part thereof and inclined upward toward the rear end thereof, and a pair of bulging portions  234  bulging forward along either side of the intermediate portion  233 . Further, the front surface of the pad member  231  is provided with a second lateral listing groove  235  extending laterally at a substantially central portion in the vertical direction, and a pair of second longitudinal listing grooves  236  extending from the upper edge to the lower edge of the pad member  231 . The second lateral listing groove  235  extends substantially between the boundaries between the intermediate portion  233  and the bulging portions  234 , and the second lateral listing groove  235  is connected to the second longitudinal listing grooves  236  at the two ends thereof, respectively. 
     The second lateral listing groove  235  and the second longitudinal listing grooves  236  each consist of a rearwardly recessed groove formed on the front surface of the pad member  231  of the seatback  205 . The second lateral listing groove  235  and the second longitudinal listing grooves  236  are provided for pulling the skin material  232  of the seat back  205  into the cushion member, similarly to the first lateral listing groove  215  and the first longitudinal listing grooves  216  mentioned earlier. 
     As shown in  FIG.  19   , a capacitance sensor  240  is positioned between the front surface of the pad member  231  of the seat back  205  and the back surface of the skin material  232 . The capacitance sensor  240  is in the form of a flexible film. The capacitance sensor  240  is a non-contact type proximity sensor that is turned on by an approaching object. More specifically, the capacitance sensor  240  is turned ON when an object having a large relative dielectric constant is located within a predetermined distance (detection distance) from the surface thereof. The object having a large relative permittivity as discussed here is an object having a relative permittivity of 10 or more, more preferably 30 or more, and includes water, a human body and the like. The detection distance is 10 cm or less, and more preferably 30 cm or less. 
     As shown in  FIG.  12   , the capacitance sensor  240  is provided along the front surface of the pad member  231  of the seat back  205 . As shown in  FIG.  11   , the capacitance sensor  240  is positioned between the left and right second longitudinal listing grooves  236 . The capacitance sensor  240  is positioned below the second lateral listing groove  235  and at a location corresponding to the occupant&#39;s hip region H (lumbar region), or in other words, behind the occupant&#39;s hip region H (see  FIG.  12   ). More precisely, the hip region H means the back part of the occupant located behind the lumbar vertebra of the occupant, and the location of the hip region is preferably determined by using a three-dimensional sitting human model for measuring the size of the vehicle interior dimensions as specified in MS D4607. 
     As shown in  FIGS.  11  and  12   , the vehicle seat  201  is provided with a determination unit  246  for determining the seating of an occupant. The determination unit  246  consists of a computer including a central processing unit (CPU) and a storage device such as memory, and includes an input unit to receive an external signal and an output unit to forward a signal to the outside. The determination unit  246  is connected to the pressure-sensitive sensor unit  219  and the capacitance sensor  240  at the input unit thereof. In the present embodiment, the determination unit  246  is attached to the lower surface of the seat cushion  204  of the vehicle seat  201 . The determination unit  246  executes a determination process to determine if the occupant is seated according to the signal from the pressure-sensitive sensor unit  219  received at the input unit (ON/OFF of the pressure-sensitive sensor unit  219 ), and the signal from the capacitance sensor  240  received at the input unit (ON/OFF of the capacitance sensor  240 ). The details of the determination process are described in the following with reference to the flowchart shown in  FIG.  15   . 
     As shown in  FIG.  15   , in the first step ST 1 , the determination unit  246  determines if the pressure-sensitive sensor unit  219  is ON or OFF. When the pressure-sensitive sensor unit  219  is ON, step ST 2  is executed, and when the pressure-sensitive sensor unit  219  is OFF, the determination process ends. 
     The determination unit  246  determines if the capacitance sensor  240  is ON or OFF in step ST 2 . The determination unit  246  executes step ST 3  when the capacitance sensor  240  is ON, and ends the determination process when the capacitance sensor  240  is OFF. 
     In step ST 3 , the determination unit  246  outputs a signal indicating that an occupant is seated from the output unit, and ends the determination process. 
     The output unit of the determination unit  246  may be connected to a control unit  248  (ECU) mounted on the vehicle body. The control unit  248  (ECU) may be, for example, a computer that controls the motion of the vehicle body. When the vehicle is driven, the control unit  248  instructs the determination unit  246  to execute the determination process, receives the signal output from the determination unit  246 , and determines if a seat belt is worn by the seated occupant as required. When the control unit  248  determines that the seat belt is not worn by the seated occupant as required, the control unit  248  may issue a warning to the occupant. 
     The effect of the vehicle seat  201  is discussed in the following. The determination unit  246  outputs a signal corresponding to the fact that the occupant is seated when the pressure-sensitive sensor unit  219  is ON and the capacitance sensor  240  is ON. In other words, the determination unit  246  determines the seating of the occupant based on the signal (ON, OFF) from the pressure-sensitive switch  220  included in the pressure-sensitive sensor unit  219  and the signal (ON, OFF) from the capacitance sensor  240 . 
     Suppose that the occupant is seated on the vehicle seat  201 , and a load is applied to the part of the seating surface  207  indicated by the shade in  FIG.  16 (A) . As a result, the second left pressure-sensitive switch pair  226 L and the second right pressure-sensitive switch pair  226 R are turned ON so that the pressure-sensitive sensor unit  219  is turned ON. As shown in  FIG.  16 (B) , when the occupant is seated more forward than in the case of  FIG.  16 (A) , the first pair of left pressure-sensitive switches  225 L and the first pair of right pressure-sensitive switches  225 R are turned on. As a result, the pressure-sensitive sensor unit  219  turns ON. As shown in  FIG.  16    (C), even when the occupant is seated more to the right than in the case of  FIG.  16    (A), the righthand-side pressure-sensitive switch  220  of the second left pressure-sensitive switch pair  226 L and the righthand-side pressure-sensitive switch  220  of the second right pressure-sensitive switch pair  226 R are turned ON. As a result, the pressure-sensitive sensor unit  219  turns ON. As discussed above, by using the pressure-sensitive sensor unit  219  in this manner, the pressure-sensitive sensor unit  219  is turned on even when the occupant is displaced either in the forward or in the lateral directions. 
     However, as shown in  FIG.  16    (D), suppose that a sack of rice (weighing about 30 kg) is placed on the seating surface  207 , and a load is applied to the portion as indicated by the shade. This causes the second left pressure-sensitive switch pair  226 L and the second right pressure-sensitive switch pair  226 R to be turned on. In this case, if the determination unit  246  makes the determination based only on the signal from the pressure-sensitive sensor unit  219 , an erroneous signal will be output. 
     However, in the present embodiment, the capacitance sensor  240  is turned on when an object having a high relative permittivity is located within a detection distance from the surface thereof. More specifically, the capacitance sensor  240  is turned ON when an object having a high relative dielectric constant, such as water or a human body, is located within a detection distance from a portion of the support surface  208  corresponding to the back of the hip region of the human body. Therefore, when the occupant (whose relative permittivity is about 40) is seated on the seating surface  207 , or when the occupant is seated as shown in any of  FIGS.  16 (A) to  16 (C) , the capacitance sensor  240  is turned ON. On the other hand, when a sack of rice (having a relative dielectric constant of about 4) is placed on the seating surface  207 , or in the case of  FIG.  16 (D) , the capacitance sensor  240  is turned OFF. As described above, since the determination unit  246  determines if the occupant is seated or not according to the signal from the pressure-sensitive switch  220  and the signal from the capacitance sensor  240 , the determination unit  246  is able to distinguish an object having a large weight and a low relative permittivity, such as a sack of rice. As described above, by configuring the determination unit  246  so as to perform the determination process based on the signal from the pressure-sensitive switch  220  and the signal from the capacitance sensor  240 , it is possible to distinguish between the case where the occupant is seated on the vehicle seat  201  and the case where an article other than a human is placed on the seating surface  207  in a reliable manner. 
     In the present embodiment, as shown in  FIG.  11   , the pressure-sensitive sensor unit  219  is provided on the seat cushion  204 , and the capacitance sensor  240  is provided on the seat back  205 . Accordingly, as compared to a case where both the pressure-sensitive sensor unit  219  and the capacitance sensor  240  are provided on the seat cushion  204 , wiring for these sensor units can be simplified, and the assembly work is facilitated. Further, since the pressure-sensitive sensor unit  219  and the capacitance sensor  240  are provided in separate members, they do not overlap with each other. Thereby, these two sensor units can be both positioned close to the seating surface  207  with which the occupant&#39;s body comes into contact at the time of seating so that the sensitivity can be improved for both the sensor units. 
     If the electrodes of the pressure-sensitive switches  220  of the pressure-sensitive sensor unit  219  are positioned near the capacitance sensor  240 , the capacitance may not be measured accurately, and the sensitivity of the capacitance sensor  240  may be impaired. Also, when the capacitance sensor  240  is located on the surface of the pressure sensor unit  219 , the weight of the capacitance sensor  240  may cause the pressure sensor unit  219  to be erroneously turned on. In the present embodiment, since the pressure-sensitive sensor unit  219  and the capacitance sensor  240  are provided in the separate members, they do not interfere with each other so that the pressure-sensitive sensor unit  219  and the capacitance sensor  240  are allowed to operate without interfering with each other. 
     As shown in  FIG.  12   , the capacitance sensor  240  is positioned so as to correspond to the hip region H of the occupant, more specifically, behind the lumbar spine of the occupant. When the occupant is seated, the hip region H of the occupant is likely to contact or approach the support surface  208  of the seat back  205 . By providing the capacitance sensor  240  at a position corresponding to the hip region H of the seated occupant, the capacitance sensor  240  can be brought closer to the body of the seated occupant. Thereby, the body of the seated occupant can be more reliably detected by the capacitance sensor  240 . 
     As shown in  FIG.  13   , the first subunit  221  and the second subunit  222  are respectively positioned ahead of and behind the first lateral listing groove  215  and between the left and right first longitudinal listing grooves  216 . By thus positioning the pressure-sensitive sensor unit  219  so as to avoid the first lateral listing groove  215  and the first longitudinal listing grooves  216 , the pressure-sensitive sensor unit  219  can be arranged without any difficulty, and the deformation and displacement of the sensor unit  219  can be avoided. Further, by arranging the first subunit  221  and the second subunit  222  separately ahead of and behind the first lateral listing groove  215 , the pressure applied to the seating surface  207  of the seat cushion  204  can be detected over a wider range. Accordingly, even when the occupant is seated on the front portion of the seating surface  207  or seated with a lateral shift, the seating of the occupant can be more reliably detected. 
     As shown in  FIG.  11   , the capacitance sensor  240  is positioned between the left and right second longitudinal listing grooves  236 . By thus arranging the capacitance sensor  240  so as to avoid the listing grooves, assembling of the capacitance sensor  240  can be facilitated, and the deformation and displacement of the capacitance sensor  240  can be avoided, 
     Fifth Embodiment 
     The vehicle seat  251  according to a fifth embodiment of the present invention differs from that of the fourth embodiment in the number and arrangement of the capacitance sensors  240 , the arrangement of the pressure-sensitive sensor units  219 , and the contents of the determination process, but is otherwise similar to that of the fourth embodiment. Therefore, the parts similar those of the previous embodiment are omitted from the following description. 
       FIG.  17    is a top view of the vehicle seats  251  with the skin material  212  removed from the left vehicle seat  251 . As shown in  FIG.  17   , each vehicle seat  251  of the fifth embodiment is provided with two capacitance sensors  253  and  254 . The two capacitance sensors  253 ,  254  are both arranged on the seat cushion  204 . More specifically, the seat cushion  204  is provided with the pressure-sensitive sensor unit  219  and the two capacitance sensors  240 . The two capacitance sensors  240  are both positioned between the front surface of the pad member  211  forming the seat cushion  204  and the back surface of the skin material  212 . 
     One of the two capacitance sensors  240  or the capacitance sensor  253  (first capacitance sensor  253 ) is positioned in front of the first lateral listing groove  215 , and between the longitudinal listing grooves  216 . The other capacitance sensor  254  (the second capacitance sensor  254 ) is positioned behind the first lateral listing groove  215  and between the first longitudinal listing grooves  216 . Thus, two capacitance sensors  253  and  254  are arranged ahead of and behind the first lateral listing groove  215  extending laterally. The first capacitance sensor  253  and the second capacitance sensor  254  are each formed in a sheet form, and has a substantially rectangular shape elongated in the lateral direction. The back surfaces of the first capacitance sensor  253  and the second capacitance sensor  254  are in surface contact with the upper surface of the pad member  211  forming the seat cushion  204 . 
     The first subunit  221  of the pressure-sensitive sensor unit  219  is arranged so as to at least partly overlap with the first capacitance sensor  253  in top view. In the present embodiment, the first subunit  221  is positioned on top of the first capacitance sensor  253  such that the first subunit  221  is located inside the outer peripheral edge of the first capacitance sensor  253  when viewed from above. The back surface of the first subunit  221  is arranged so as to be in surface contact with the first capacitance sensor  253 . 
     The second subunit  222  of the pressure-sensitive sensor unit  219  is arranged so as to at least partly overlap with the second capacitance sensor  254  in top view. In the present embodiment, the second subunit  222  is positioned on top of the second capacitance sensor  254 , and the second subunit  222  is located inside the outer peripheral edge of the second capacitance sensor  254  when viewed from above. The back surface of the second subunit  222  is arranged so as to be in surface contact with the second capacitance sensor  254 . 
     The determination unit  246  determines if an occupant is seated from the ON/OFF state of the pressure-sensitive sensor unit  219  and the ON/OFF states of the two capacitance sensors  240  received from the input unit. The determination process executed by the determination unit  246  for the vehicle seat  251  according to the fifth embodiment is different from the fourth embodiment only in step ST 2  so that the description of the other parts of the determination process is omitted from the following description. 
     In step ST 2 , the determination unit  246  determines if one of the first capacitance sensor  253  and the second capacitance sensor  254  is ON. If at least one of these two capacitance sensors is ON, step ST 3  is executed. When both the first capacitance sensor  253  and the second capacitance sensor  254  are OFF, the determination process ends. 
     The effect of the vehicle seat  251  configured as described above is discussed in the following. The two capacitance sensors  240  are both provided so as to be close to the seating surface  207  of the seat cushion  204  on which the occupant sits. Since the seating surface  207  is a region where the seated occupant is highly likely to be in contact with, the two capacitance sensors  240  are likely to be brought closer to the seated occupant. This allows the capacitance sensors  240  to more accurately detect the occupant&#39;s seating. 
     Further, the first subunit  221  and the first capacitance sensor  253  are arranged so as to overlap each other when viewed from above, and the second subunit  222  and the second capacitance sensor  254  similarly overlap with each other. Therefore, the surface area of the pad member  211  of the seat cushion  204  where the pressure-sensitive sensor unit  219  and the capacitance sensor  240  are arranged can be reduced. By arranging the pressure-sensitive sensor unit  219  and the capacitance sensor  240  in this manner, any discomfort to the seat occupant can be minimized. 
     In the present embodiment, further, the first subunit  221  is positioned inside the outer periphery of the first capacitance sensor  253 , and the second subunit  222  is positioned inside the outer periphery of the second capacitance sensor  254 . Owing to this arrangement, the area over which the pressure-sensitive sensor unit  219  and the capacitance sensor  240  overlap with each other can be further increased. Accordingly, the surface area of the pad member  211  of the seat cushion  204  where the pressure-sensitive sensor unit  219  and the capacitance sensor  240  are arranged can be minimized so that the discomfort to the seat occupant can be further reduced. 
     The first capacitance sensor  253  and the second capacitance sensor  254  are positioned ahead of and behind the first lateral listing groove  215 , respectively, and between the left and right first longitudinal listing grooves  216 . Accordingly, the first capacitance sensor  253  and the second capacitance sensor  254  can be arranged so as to avoid the first lateral listing groove  215  and the first longitudinal listing grooves  216 . As a result, the assembling of the pressure-sensitive sensor unit  219  and the two capacitance sensors  253  and  254  can be facilitated, and the deformation and displacement of the pressure-sensitive sensor unit  219  and the two capacitance sensors  253  and  254  can be minimized. Since the first capacitance sensor  253  and the second capacitance sensor  254  are arranged ahead of and behind the first lateral listing groove  215 , respectively, the first capacitance sensor  253  is turned on when the occupant is seated in a front part of the seating surface  207  while the second capacitance sensor  254  is turned on when the occupant is seated in a rear part of the seating surface  207 . As a result, the seating of a seat occupant over a wide range in the fore and aft direction can be detected. 
     Sixth Embodiment 
     The vehicle seat  261  according to a sixth embodiment of the present invention is different from the vehicle seat  201  of the fifth embodiment in the shape of the first capacitance sensor  253  and the second capacitance sensor  254 , but is otherwise similar to the vehicle seat of the fifth embodiment. Therefore, other parts of the vehicle seat  261  of the sixth embodiment are omitted from the following description. 
       FIG.  18    is a top view of two vehicle seats  261  of which the left vehicle seat  261  is shown with a part of the skin material  212  removed therefrom. As shown in  FIG.  18   , the first capacitance sensor  253  and the second capacitance sensor  254  are each in a sheet form of a substantially rectangular shape elongated in the lateral direction. Each of the first capacitance sensor  253  and the second capacitance sensor  254  is provided with an opening  263  and  264  passed vertically therethrough. The openings  263  and  264  each have a substantially rectangular shape elongated in the lateral direction. 
     The first capacitance sensor  253  is located in front of the first lateral listing groove  215  and between the first longitudinal listing grooves  216  laterally spaced from each other. The second capacitance sensor  254  is positioned behind the first lateral listing groove  215  and between the first longitudinal listing grooves  216 . Therefore, the two capacitance sensors  253  and  254  having the openings  263  and  264  are respectively arranged ahead of and behind the first lateral listing groove  215  extending laterally. The back surfaces of the first capacitance sensor  253  and the second capacitance sensor  254  are in surface contact with the upper surface of the pad member  211  of the seat cushion  204 . 
     The first subunit  221  is positioned inside the opening  263  of the first capacitance sensor  253 . The back surface of the first subunit  221  is in surface contact with the pad member  211  of the seat cushion  204 . In the present embodiment, the thickness of the first subunit  221  and the thickness of the first capacitance sensor  253  are substantially equal to each other so that the upper surface of the first subunit  221  and the upper surface of the first capacitance sensor  253  are flush with each other. 
     The second subunit  222  is positioned inside the opening  264  of the second capacitance sensor  254 . The back surface of the second subunit  222  is in surface contact with the pad member  211  of the seat cushion  204 . In the present embodiment, the thickness of the second subunit  222  is substantially equal to the thickness of the second capacitance sensor  254  so that the upper surface of the second subunit  222  and the upper surface of the second capacitance sensor  254  are flush with each other. 
     The first capacitance sensor  253 , the second capacitance sensor  254 , the first subunit  221  and the second subunit  222  are all positioned between the pad member  211  of the seat cushion  204  and the skin material  212 . 
     The effect of the vehicle seat  261  configured as described above is discussed in the following. The first subunit  221  is positioned inside the opening  263  of the first capacitance sensor  253  so that a step is less likely to be produced between the upper surface of the first subunit  221  and the upper surface of the first capacitance sensor  253 . Similarly, the second subunit  222  is positioned inside the opening  264  of the second capacitance sensor  254  so that a step is less likely to be produced between the upper surface of the second subunit  222  and the upper surface of the second capacitance sensor  254 . As a result, a step is less likely to be produced on the seating surface  207  so that the seating comfort can be improved. In this embodiment, the upper surface of the first subunit  221  and the upper surface of the first capacitance sensor  253  are flush with each other, and the upper surface of the second subunit  222  and the upper surface of the second capacitance sensor  254  are also flush with each other so that the seating surface  207  can be made of a highly even planar surface. Thereby, the sitting comfort can be further improved. 
     The first capacitance sensor  253  and the second capacitance sensor  254  are positioned between the left and right first longitudinal listing grooves  216  and ahead of and behind the first lateral listing groove  215 , respectively. Therefore, the two capacitance sensors  253  and  254  can be positioned so as to avoid the first lateral listing groove  215  and the first longitudinal listing grooves  216 . As a result, the assembling of the capacitance sensors  253  and  254  can be facilitated, and deformation and displacement of the pressure-sensitive sensor unit  219  and the two capacitance sensors  253  and  254  can be minimized. Further, by arranging the two capacitance sensors  253  and  254  in front of and behind the first lateral listing groove  215 , respectively, the occupant&#39;s seating can be detected over a wider range in the fore and aft direction. 
     Seventh Embodiment 
     The vehicle seat  271  according to a seventh embodiment of the present invention differs from the vehicle seat  201  of the fourth embodiment only in the positioning of the capacitance sensor  240  and the structure and positioning of the pressure-sensitive sensor unit  219 , but is otherwise similar to the vehicle seat  201  of the fourth embodiment. Therefore, the remaining parts of the vehicle seat  271  are omitted from the following description. 
       FIG.  19    is a top view of two vehicle seats  271  of which the left vehicle seat  271  is shown with a part of the skin material  212  removed therefrom. As shown in  FIG.  19   , the capacitance sensor  240  is placed between the front surface of the pad member  211  of the seat cushion  204  and the back surface of the skin material  212  of the seat cushion  204 . The capacitance sensor  240  is positioned on the surface of the pad member  211  in front of the first lateral listing groove  215  and between the left and right first longitudinal listing grooves  216 . The back surface of the capacitance sensor  240  is in surface contact with the front surface of the pad member  211  of the seat cushion  204 . 
     Unlike the preceding embodiment, the pressure-sensitive sensor unit  219  does not include a second subunit  222 , and instead consists solely of the first subunit  221 . When the first left pressure-sensitive switch pair  225 L is ON and the first right pressure-sensitive switch pair  225 R is ON, the pressure-sensitive sensor unit  219  is turned ON. 
     The pressure sensor unit  219  (the first subunit  221 ) is also provided between the front surface of the pad member  211  of the seat cushion  204  and the back surface of the skin material  212  of the seat cushion  204 . The pressure-sensitive sensor unit  219  is positioned behind the first lateral listing groove  215  and between the left and right first longitudinal listing grooves  216 . The back surface of the pressure-sensitive sensor unit  219  is in surface contact with the front surface of the pad member  211  of the seat cushion  204 . 
     The effect of the vehicle seat  271  thus configured is discussed in the following. Since both the pressure-sensitive sensor unit  219  and the capacitance sensor  240  are positioned near the seating surface  207 , the seating of an occupant can be detected with a higher sensitivity. In addition, since the pressure-sensitive sensor unit  219  and the capacitance sensor  240  are positioned so as to avoid the first lateral listing groove  215  and the first longitudinal listing grooves  216 , the assembling of these sensors to the seat cushion  204  is facilitated. Further, deformation and displacement of the pressure-sensitive sensor unit  219  and the capacitance sensor  240  when the occupant is seated can be minimized. Further, by positioning the pressure-sensitive sensor unit  219  behind the first lateral listing groove  215 , the load of the occupant can be made more likely to be transmitted to the pressure-sensitive sensor unit  219 , as compared with the case where the pressure-sensitive sensor unit  219  is positioned in front of the first lateral listing groove  215 , so that the detection of the seating of an occupant can be detected in a more reliable manner. 
     The present invention has been described in terms of specific embodiments, but is not limited by such embodiments, and can be modified in various ways without departing from the scope of the present invention. For example, in the first embodiment and the second embodiment, the recess  45  may be provided in the floor portion  5  instead of the back surface of the seat cushion pad  11 . In other words, the recess  45  may be provided on one of the back surface of the seat cushion pad  11  and the floor portion  5 . Similarly, the recess  45  may be provided on one of the back surface of the seat back pad  51  and the wall portion  6 . 
     In the first embodiment and the second embodiment, the open end of the wire harness passage  35  on the front surface side may also be provided inside the listing groove. The open end on the front surface side of the wire harness passage  35  may be provided in any one of the left and right longitudinal grooves and the front and rear lateral grooves. 
     In the third embodiment, the ninth branch part  111 K may also extend rearward from the center of the main part  111 A. In this case, the connecting portion  114  may be provided at the rear end of the ninth branch part  111 K, and the connecting portion  114  may be positioned ahead of the first imaginary straight line L 1 . The ninth branch part  111 K may extend leftward from the left end of the main part  111 A, and may extend rightward from the right end of the main part  111 A. Each branch part  111 B to  111 K may be curved or bent. 
     In the fifth embodiment, the pressure-sensitive sensor unit  219  and the capacitance sensor  240  are provided separately, but the pressure-sensitive switch  220  and the capacitance sensor  240  may also be provided on one sheet-like member. In the foregoing embodiments, the determination unit  246  is attached to the lower surface of the seat cushion  204 , but the present invention is not limited to this mode. For example, the determination unit  246  may be placed on a predetermined position on the floor  203 , or may be formed by software incorporated in the control unit  248 . 
     LIST OF REFERENCE NUMERALS 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                  1: 
                 seat of a first embodiment 
               
               
                   
                  2: 
                 seat cushion 
               
               
                   
                  3: 
                 seat back 
               
               
                   
                  4: 
                 body panel 
               
               
                   
                  5: 
                 floor portion 
               
               
                   
                  6:  
                 wall portion 
               
               
                   
                  11: 
                 seat cushion pad 
               
               
                   
                  12: 
                 skin material 
               
               
                   
                  14: 
                 rigid part 
               
               
                   
                  15: 
                 soft part 
               
               
                   
                  20: 
                 listing groove 
               
               
                   
                  28: 
                 rear inclined portion 
               
               
                   
                  30: 
                 pressure receiving area 
               
               
                   
                  32: 
                 sensor 
               
               
                   
                  33: 
                 wire harness 
               
               
                   
                  35: 
                 wire harness passage 
               
               
                   
                  37: 
                 air passage 
               
               
                   
                  41: 
                 locking portion 
               
               
                   
                  45: 
                 recess 
               
               
                   
                  51: 
                 seat back pad 
               
               
                   
                  52: 
                 skin material 
               
               
                   
                  57: 
                 sensor 
               
               
                   
                  58: 
                 wire harness passage 
               
               
                   
                  59: 
                 wire harness 
               
               
                   
                  61: 
                 recess 
               
               
                   
                  70: 
                 seat of a second embodiment 
               
               
                   
                  72: 
                 heater cloth 
               
               
                   
                 101: 
                 seat of a third embodiment 
               
               
                   
                 102: 
                 seat cushion 
               
               
                   
                 105: 
                 seating region 
               
               
                   
                 106: 
                 seat cushion pad 
               
               
                   
                 107: 
                 skin material 
               
               
                   
                 110: 
                 seat sensor 
               
               
                   
                 111: 
                 sheet material 
               
               
                   
                 111A: 
                 the main part 
               
               
                   
                 111B to 111K: 
                 first to ninth branch parts 
               
               
                   
                 112B to 112J: 
                 first to eighth pressure-sensitive switches 
               
               
                   
                 113: 
                 wiring 
               
               
                   
                 114: 
                 connecting portion 
               
               
                   
                 116: 
                 first circuit 
               
               
                   
                 117: 
                 second circuit 
               
               
                   
                 118: 
                 third circuit 
               
               
                   
                 119: 
                 fourth circuit 
               
               
                   
                 122: 
                 control unit 
               
               
                   
                 201: 
                 vehicle seat of a fourth embodiment 
               
               
                   
                 204: 
                 seat cushion 
               
               
                   
                 205: 
                 seat back 
               
               
                   
                 206: 
                 headrest 
               
               
                   
                 215: 
                 first lateral listing groove 
               
               
                   
                 220: 
                 pressure-sensitive switch (pressure sensor) 
               
               
                   
                 236: 
                 second longitudinal listing groove 
               
               
                   
                 240: 
                 capacitance sensor 
               
               
                   
                 246: 
                 determination unit 
               
               
                   
                 251: 
                 vehicle seat of a fifth embodiment 
               
               
                   
                 253: 
                 first capacitance sensor 
               
               
                   
                 254: 
                 second capacitance sensor 
               
               
                   
                 261: 
                 vehicle seat of a sixth embodiment 
               
               
                   
                 263, 264: 
                 opening 
               
               
                   
                 271: 
                 vehicle seat of a seventh embodiment 
               
               
                   
                 HP: 
                 hip point 
               
               
                   
                 L1: 
                 first imaginary straight line 
               
               
                   
                 L2: 
                 second imaginary straight line 
               
               
                   
                 H: 
                 hip