Abstract:
The heating elements of a seat heater are used to warm the occupant seated on the seat and also used to detect the occupant. The configuration eliminates the need to dispose, in the vicinity of the seating surface of the seat, both a heater unit used for warming the occupant and a sensor for detecting the occupant. As a result, the structure of the seat is simplified to prevent deterioration in seating comfort, and at the same time, the occupant can be accurately detected and the heating elements can be efficiently utilized.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national phase application filed under 35 U.S.C. §371 of International Application PCT/JP2011/067167, filed on Jul. 27, 2011, designating the United States, which claims priority from Japanese Application 2010-176821, filed Aug. 5, 2010, which are hereby incorporated herein by reference in their entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a heating system, and more particularly, to a heating system for warming an occupant seated on a seat. 
     BACKGROUND OF THE INVENTION 
     Occupant restraining systems represented by seat belts and air-bag systems have become smaller and of lower cost, and are nowadays installed in almost all kinds of vehicles as standard equipment. This kind of occupant restraining system should be able to detect the occupant of a seat with accuracy for urging him/her to wear the seat belt or for controlling the air-bag according to the presence/absence of the occupant. 
     On the other hand, vehicles used in cold climates sometimes have a heating element installed in the seats for warming the occupants. The seats of vehicles generally have a seating surface made of a low heat conductive material such as urethane foam. Therefore, for warming the occupant efficiently, the heating element should be placed near the seating surface. 
     Then, a two-tier structure unit formed by laminating a heating element film and a sensor film has been proposed (for example, see Japanese National Patent Publication No. 2004-504082). Using this unit, a sensor for detecting the occupant and a heating element for warming the occupant can be placed near the seating surface. Consequently, it is possible to warm the occupant seated on the seat efficiently and detect the occupant with accuracy. 
     SUMMARY OF THE INVENTION 
     However, with the above unit, both the heating element and the sensor are placed near the seating surface. Therefore, use of the above unit may inconveniently cause the seat to be uncomfortable to sit in. 
     A possible solution to eliminate this inconvenience is to provide a sensor electrode for detecting the presence/absence of an occupant and a wire of heating element on a common film in the manner that they do not overlap with each other. However, a relatively large current flows through the heating element. Therefore, some noise may intrude into the electric circuit sensing the occupant when a current starts or stops flowing through the heating element. 
     In consideration of the foregoing, it is an objective of the present invention to efficiently use the heating element and accurately detect the occupant while improving the comfort of the seat. 
     In order to achieve the above objective, a heating system according to a first aspect of the present invention is:
         a heating system for warming an occupant seated on a seat of a vehicle, the heating system comprising:   a heating element disposed in the seat;   a heater unit for passing electricity to the heating element via electrodes connected to the heating element, causing heat to be generated from the heating element;   measurement means for measuring impedance between the electrodes and the vehicle;   detection means for detecting the occupant seated on the seat based on the impedance measured by the measurement means; and   switching means for alternately connecting the heater unit and the measurement means to the electrodes.       

     A heating system according to a second aspect of the present invention is:
         a heating system for warming an occupant seated on a seat of a vehicle, the heating system comprising:   a heating element disposed in the seat;   a heater unit for passing electricity to the heating element via a first electrode and a second electrode connected to the heating element, causing heat to be generated from the heating element;   measurement means for measuring impedance between the first electrode and the vehicle, and impedance between the second electrode and the vehicle;   detection means for detecting the occupant seated on the seat based on the impedance measured by the measurement means; and   switching means for alternately connecting the heater unit and the measurement means to the first electrode and the second electrode.       

     The measurement means may measure, as an impedance-correlated value, the capacitance between the electrodes and the vehicle from the electric current or voltage input to the electrodes, in concert with changes in the impedance and AC voltage applied between the electrodes and the vehicle. 
     The measurement means may measure the quadrature component of the electric current with respect to the AC voltage as the capacitance as an impedance-correlated value. 
     The measurement means may measure the in-phase component of the electric current with respect to the AC voltage; and
         the detection means may detect the occupant seated on the seat from a comparison result of the capacitance and a threshold value set from a relationship between the in-phase component and the quadrature component.       

     The heating system may further comprise temperature detection means for detecting the temperature of the seat near the heating element based on the resistance of the heating element;
         wherein the detection means detects the occupant based on the comparison result of the capacitance and the threshold value, and the temperature of the seat detected by the temperature detection means.       

     The heating system may further comprise a temperature detection sensor for detecting the temperature of the seat near the heating element;
         wherein the detection means detects the occupant based on the comparison result of the capacitance and the threshold value, and the temperature of the seat detected by the temperature detection sensor.       

     The measurement means may measure the in-phase component of the electric current relative to the AC voltage; and
         the heater unit may pass electricity to the heating element when the ratio of the in-phase component is at least a threshold value.       

     The heating system may further comprise abnormality detection means for detecting abnormalities in the heating elements based on the phase difference between the phase of the electric current of the first electrode relative to the voltage applied on the first electrode and the phase of the electric current of the second electrode relative to the voltage applied on the second electrode. 
     The heater unit may pass electricity to the heating element when the occupant has been detected based on a detection result of the detection means. 
     According to the present invention, it is possible to use a heating element to warm an occupant seated on a seat and also as a sensor for detecting the occupant. Consequently, the structure of the unit positioned near the surface of the seat is simplified. Through this, it becomes possible to accurately detect an occupant and to efficiently use the heating element while maintaining the comfort of the seat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a heating system according to a preferred embodiment; 
         FIG. 2  is a planar view showing a seat heater; 
         FIG. 3  is a cross-sectional view of the seat heater at a line A-A in  FIG. 2 ; 
         FIG. 4  is an illustration showing a vehicle seat and the occupant seated on the seat; 
         FIG. 5  is a diagram schematically showing the electric circuit formed when there is no occupant seated on the seat; 
         FIG. 6  is a diagram showing an equivalent circuit to the electric circuit in  FIG. 5 ; 
         FIG. 7  is a diagram schematically showing the electric circuit formed when there is an occupant seated on the seat; 
         FIG. 8  is a diagram showing an equivalent circuit to the circuit in  FIG. 7 ; 
         FIG. 9  is a diagram showing an equivalent circuit between an electrode and body; 
         FIG. 10  is a graphical representation showing a relationship between the quadrature component and the in-phase component; 
         FIG. 11  is a block diagram of a heating system according to a modified embodiment; and, 
         FIG. 12  is a diagram showing the seat heater according to a modified embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment of the present invention will be described hereafter with reference to the drawings.  FIG. 1  is a block diagram of a heating system  10  according to the preferred embodiment. The heating system  10  is, for example, a system for warming an occupant seated on a seat of a vehicle. As shown in  FIG. 1 , the heating system  10  has a seat heater  20 , a changeover switch  31 , a heater unit  32  and a detection unit  33 . 
       FIG. 2  is a planar view showing the seat heater  20 . In addition,  FIG. 3  is a cross-sectional view of the seat heater at a line A-A in  FIG. 2 . As shown in  FIGS. 2 and 3 , the seat heater  20  has a first electrode  21 , a second electrode  22 , heating elements  23  and  24 , and insulation sheets  25  and  26  covering the above-described first electrode  21 , second electrode  22  and heating elements  23  and  24 . 
     The insulation sheet  25  is, for example, a sheet formed of a PET (polyethylene tephthalate), or a Mylar film. Moreover, the insulation sheet  25  which is a sheet formed of a material with flexibility like polyimide, polyvinyl chloride, or a silicon rubber can be applied. This insulation sheet  25  is shaped into a rectangle having a lengthwise direction in a Y-axis direction. 
     The first electrode  21  is formed on the top surface (the surface on the +Z side) of the insulation sheet  25 . The first electrode  21  is made of a silver paste or copper, and is composed of wiring  21   a  patterned in a U-shape, and a terminal  21   b  extending in the −y direction from the wiring  21   a.    
     Similar to the first electrode  21 , the second electrode  22  is composed of wiring  22   a  formed in a U-shape, and an L-shaped terminal  22   b  connected to the wiring  22   a . The part of the wiring  22   a  comprising the second electrode  22  on the +x side encloses the wiring  21   a  of the first electrode  21 . 
     The first electrode  21  and the second electrode  22  can be formed by coating and hardening silver paste on the top surface of the insulation sheet  25 , or can be formed by adhering copper foil to the insulation sheet  25  and then etching and patterning the copper foil. 
     The heating elements  23  and  24  are each shaped into a rectangular shape with the lengthwise direction being in the Y-axis direction. These heating elements  23  and  24  are positioned so as to be adjacent in the X-axis direction. As shown in  FIG. 3 , the heating elements  23  and  24  are each formed from the top surface of the first electrode to the top surface of the second electrode  22 . 
     These heating elements  23  and  24  are formed on the top surface of the insulation sheet  25  by coating and hardening temperature-sensitive resistor paste or carbon paste from the first electrode  21  to the second electrode  22  on the top surface of the insulation sheet  25  on which the first electrode  21  and the second electrode  22  are formed. With temperature-sensitive resistor paste, the resistance value changes depending on the temperature of the paste itself. Consequently, when temperature-sensitive resistor paste is used as the material of the first electrode  21  and the second electrode  22 , the electric current flowing through the first electrode  21  and the second electrode  22  is self-regulated by the temperature-sensitive resistor paste. 
     The insulation sheet  26  is a sheet made of the same kind of material as the insulation sheet  25 . The insulation sheet  26  is shaped into the same shape as the insulation sheet  25 , and is fastened with an adhesive and/or the like to the top surface of the insulation sheet  25 . Through this, the first electrode  21  and the second electrode  22  formed on the top surface of the insulation sheet  25 , and the heating elements  23  and  24 , are covered. 
       FIG. 4  is an illustration showing a seat  101  of a vehicle along with an occupant  120  seated on the seat  101 . As shown in  FIG. 4 , the seat heater  20  comprised as described above is positioned directly below the seat cover comprising the seating surface  101   a  of the seat  101 . 
     Returning to  FIG. 1 , the changeover switch  31  is a switch that alternately connects the seat heater  20  to the heater unit  32  and the detection unit  33 . The changeover switch  31  has six terminals t 1  to t 6 . Furthermore, the terminal t 1  is connected to the first electrode  21  of the seat heater  20  and the terminal t 2  is connected to the second electrode  22 . In addition, the terminal t 3  and the terminal t 5  are connected to the heater unit  32 , and the terminal t 4  and the terminal t 6  are connected to the detection unit  33 . 
     The changeover switch  31  repeats the action of connecting the terminal t 1  to the terminal t 3  and the terminal t 2  to the terminal t 5 , and the action of connecting the terminal t 1  to the terminal t 4  and the terminal t 2  to the terminal t 6 , with a preset period. Through this, the seat heater  20  is alternately connected to the heater unit  32  and the detection unit  33 . 
     The heater unit  32 , while connected to the seat heater  20 , supplies the seat heater  20  with electrical energy from an unrepresented battery provided in the vehicle. Through this, an electric current flows through the heating elements  23  and  24  of the seat heater  20 , and the heating elements  23  and  24  emit heat. 
     The detection unit  33 , while connected to the seat heater  20 , finds the AC impedance between the first electrode  21  and second electrode  22  and the vehicle, and determines whether or not the occupant  120  is seated on the seat  101  based on the AC impedance found. Furthermore, the detection unit  33  outputs the result determined to an external device, for example. 
       FIG. 5  is a diagram schematically showing the electric circuit formed when the occupant  120  is seated on the seat  101 . In the electrical circuit formed when the occupant is not seated on the seat  101 , the first electrode  21  and the body  100  are connected by an AC resistor R 1  and a capacitor C 1 , as shown in  FIG. 5 . In addition, the second electrode  22  and the body  100  are connected by an AC resistor R 2  and a capacitor C 2 . In addition, the heating elements  23  and  24  are connected by an AC resistor R 3  and a capacitor C 3 . 
       FIG. 6  is an equivalent circuit to the circuit shown in  FIG. 5 . The circuit shown in  FIG. 5  can be replaced by the equivalent circuit shown in  FIG. 6 . A resistor Ra comprising the equivalent circuit in  FIG. 6  shows the resistance between the first electrode  21  and the second electrode  22 . Furthermore, a resistor Rb is a combined resistance of resistors R 1  to R 3 . The resistance value of resistors R 1  to R 3  is determined by the seat materials and is remarkably large. Consequently, the resistance value of the resistor Rb that is a combined resistance of the resistors R 1  to R 3  becomes remarkably larger than the resistance value of the resistor Ra. In addition, the capacitor Ca and the capacitor Cb comprising the equivalent circuit of  FIG. 6  are a composite of the capacitors C 1  to C 3 . 
     As can be seen by referring to the equivalent circuit of  FIG. 6 , the composite capacitance C T1  between the seat heater  20  and the body  100  can be measured from formula (1) below. In formula (1) below, Ca and Cb mean the capacitance of the capacitors Ca and Cb.
 
 C   T1   =Ca+Cb   (1)
 
       FIG. 7  is a diagram schematically showing an electrical circuit formed when the occupant  120  is seated on the seat  101 . As can be understood by comparing  FIG. 7  and  FIG. 5 , when the occupant  120  is seated on the seat  101 , a new circuit interposed by the occupant  120  is formed. This newly formed circuit comprises a capacitor C 4  showing the capacitance between the first electrode  21  and the occupant  120 , a capacitor C 5  showing the capacitance between the second electrode  22  and the occupant  120 , a capacitor C 6  showing the capacitance between the heating elements  23  and  24  and the occupant  120 , a capacitor C 7  showing the capacitance between the occupant  120  and the body  100 , and a resistor R 4  showing the resistance between the occupant  120  and the body  100 . 
       FIG. 8  is an equivalent circuit to the circuit shown in  FIG. 7 . The circuit shown in  FIG. 7  can be replaced by the equivalent circuit shown in  FIG. 8 . A capacitor Cc and a capacitor Cd comprising the equivalent circuit of  FIG. 8  are composites of capacitors C 4  to C 6 . 
     As can be seen by referencing the equivalent circuit of  FIG. 8 , when the occupant  120  is seated on the seat  101 , the composite capacitance C T2  between the seat heater  20  and the body  10  can be measured from formula (2) below. In formula (2) below, Cc, Cd and C 7  mean the capacitance of the capacitors Cc, Cd and C 7 .
 
 C   T2   =C   T1 +( Cc+Cd )· C 7/( Cc+Cd+C 7)  (2)
 
     As can be seen from formula (2), when the occupant  120  is seated on the seat  101 , the value of the composite capacitance increases by the amount of the capacitance from the capacitors Cc, Cd and C 7 . The detection unit  33  detects the composite capacitance that changes as described above, and based on the detected result determines whether or not the occupant  120  is seated on the seat  101 . The specific composition of the detector is described below. 
     For example, as shown in  FIG. 8  the detection unit  33  has an AC power source  33   a , a quadrature demodulator  33   b  and a detector  33   c.    
     The AC power source  33   a  converts the voltage of the unrepresented battery provided in the vehicle into an AC voltage of around 100 kHz, and applies such on the first electrode  21  and the second electrode  22  and on the body  100 . 
     The quadrature demodulator  33   b  monitors the voltage V between the first electrode  21  and the second electrode  22  and the body  100 , and the electric current i supplied to the first electrode  21  and the second electrode  22 . Furthermore, the quadrature demodulator  33   b  outputs to the detector  33   c  information relating to the in-phase component I of the electric current i relative to the voltage V, and the quadrature component Q of the electric current i relative to the voltage V. 
     The detector  33   c  determines whether or not the occupant  120  is seated on the seat  101  based on the value of the in-phase component I and the quadrature component Q. Furthermore, the detector  33   c  outputs the result determined to an external device and/or the like, for example. 
     The electric circuits shown in  FIGS. 6 and 8  as one example can be considered as the circuit shown in  FIG. 9 . In this case, the impedance between the first electrode  21  and second electrode  22  and the body  100 , that is to say, the composite resistance R T  and the composite capacitance C T , are respectively shown by formula (3) and formula (4) below. With formula (3) below, the composite capacitance C T  can be seen to be equivalent to the quadrature component Q.
 
 C   T   =Q   (3)
 
 R   T =1/ I   (4)
 
     Hence, the detector  33   c  compares, for example, the value of the quadrature component Q with a predetermined threshold value. Next, when the quadrature component Q is equal to or larger than the threshold value, the detector  33   c  determines that the occupant  120  is seated on the seat  101 . Conversely, when the quadrature component Q is smaller than the predetermined threshold value, the detector  33   c  determines that no occupant  120  is seated on the seat  101 . 
     According to the present embodiment, when the seating surface  101   a  of the seat  101  is wet or when the material of the seat  101  is moist, the above-explained threshold is set in consideration of the increase of the capacitance between the sensor electrode  25  and the vehicle  100 . To set such a threshold, a straight line indicating an IQ characteristic shown in  FIG. 10  is utilized. 
     A straight line L 1  in  FIG. 10  shows a relationship between the quadrature component Q and the in-phase component I when the occupant  120  is not seated on the seat  101 . In addition, a straight line L 2  shows the relationship between the quadrature component Q and the in-phase component I when the occupant  120  is seated on the seat  101 . The detector  33   c  determines the threshold value based on a straight line L 3  between the straight line L 1  and the straight line L 2 . For example, when the value of the in-phase component I is a, the detector  33   c  determines the threshold value to be b. Furthermore, when the value of the quadrature component Q is a value larger than the threshold value b, for example Q 2 , the detector  33   c  determines that the occupant  120  is seated on the seat  101 . On the other hand, when the value of the quadrature component Q is a value smaller than the threshold value b, for example Q 1 , the detector  33   c  determines that the occupant  120  is not seated on the seat  101 . Furthermore, the detector  33   c  outputs information related to the result of the above-described determination to an external device, for example. 
     The relationship between the in-phase component I and the quadrature component Q when the passenger is seated differs depending on the shape and material of the seat or the temperature, and is not necessarily expressed by a straight line as shown in  FIG. 10 . In this case, it is possible to accurately determine the threshold value by making the straight line L 3  determining the threshold value a polyline or curve in accordance with polylines or curves showing the relationship between the in-phase component I and the quadrature component Q. In addition, by also revising the threshold value in accordance with temperature, it is possible to accurately determine the threshold value. 
     The external device can use the determination result, for example, for giving a warning to wear the seatbelt or for controlling the expansion of the air-bag. 
     As explained above, with this preferred embodiment, the seat heater  20  positioned near the seating surface  101   a  of the seat  101  is used to warm the occupant  120  seated on the seat  101  and also to detect the occupant  120  seated on the seat  101 . Consequently, it is not necessary to position both a heater unit used for warming the occupant  120  and a sensor for detecting the occupant  120  near the seating surface  101   a  of the seat  101 , for example. Accordingly, the composition of the seat  101  does not become complex and the comfort of the seat  101  is not lost. 
     In addition, the heating elements  23  and  24  of the seat heater  20  of the preferred embodiment are used to warm the occupant  120  and are also used to detect the occupant  120  seated on the seat  101 . Consequently, the structure of the seat heater  20  is simplified. Accordingly, it is possible to reduce the cost of the seat heater  20  and consequently it is possible to realize the heating system  10  at low cost. 
     In addition, with the preferred embodiment both the first electrode  21  and the second electrode  22  are connected to the detection unit  33 , as shown in  FIG. 1 , for example. Consequently, the potentials of the first electrode  21  and the second electrode  22  are the same. Accordingly, even when the resistance of the heating elements  23  and  24  change due to the temperatures of the heating elements  23  and  24  rising, or when the difference between the resistance of the heating element  23  and the resistance of the heating element  24  becomes large, the detection unit  33  can accurately detect the occupant  120  seated on the seat  101  without being influenced by the resistance values of the heating elements  23  and  24 . 
     In addition, with the preferred embodiment the threshold value for determining whether or not the occupant  120  is seated on the seat  101  based on the value of the in-phase component I output from the quadrature demodulator  33   b  is corrected. Accordingly, it is possible to detect the occupant  120  with good accuracy. 
     The embodiments of the present invention were explained above, but the present invention is not limited to the above-explained embodiments. For example, according to the above-explained embodiments, information on the determination result by the detection unit  33  is output to the external device. The present invention is not limited to this configuration, and the information on the determination result by the detection unit  33  may be output to the heater unit  32 , for example as shown in  FIG. 11 . This allows the heater unit  32  to stop energizing the heater electrodes  21  and  22  when, for example, no occupant  120  is seated on the seat  101 . This suppresses unnecessary power consumption. 
     Moreover, the heater unit  32  may obtain information on the in-phase component I from the detection unit  33 , and may determine that the seat  101  is moistened when the in-phase component I exceeds a threshold to continue energizing the heater electrodes  21  and  22 . According to such a configuration, the drying of the seat  101  can be prompted, thereby improving the detection precision of the occupant  120  seated on the seat  101 . 
     In addition, as shown in  FIG. 12 , a temperature-sensitive resistor PT for detecting the temperature of the seat  101  may be formed on the top surface of the insulation sheet  25 . Through this, the detection unit  33  can detect the temperature of the seat  101  from the resistance of the temperature-sensitive resistor PT found via the second electrode  22  and a third electrode  27 , and can correct the threshold value for determining whether or not the occupant  120  is seated on the seat  101  taking the detected temperature into consideration. 
     In addition, the detection unit  33  may detect the temperature of the seat  101  from the resistance of the heating elements  23  and  24  found via the first electrode  21  and the second electrode  22 , and may correct the threshold value for determining whether or not the occupant  120  is seated on the seat  101  taking the detected temperature into consideration. 
     In addition, the heater unit  32  may accomplish a disconnection diagnosis by finding the resistance values of the heating elements  23  and  24  when electric current is passing, for example. In addition, the detection unit  33  may accomplish a disconnection diagnosis based on the quadrature component Q and the in-phase component I. The resistance values of the heating elements  23  and  24  change depending on the temperature, so a failure diagnosis could be difficult when only finding the resistance values of the heating elements  23  and  24 . However, by monitoring changes in the quadrature component Q and the in-phase component I, it is possible to accurately diagnose failures such as disconnection of the seat heater  20 . 
     In addition, with the above-described preferred embodiment, both the first electrode  21  and the second electrode  22  were connected to the detection unit  33 , for example as shown in  FIG. 1 . This is not intended to be limiting, for one out of the first electrode  21  and the second electrode  22  may be connected to the detection unit  33 . In this case also, it is possible to detect the occupant  120  seated on the seat  101 . 
     In addition, the first electrode  21  and the second electrode  22  may be alternately connected to the detection unit  33 . In this case, it is possible detect abnormalities between the first electrode  21  and the second electrode  22  by comparing the phase of the electric current with respect to the voltage applied on the first electrode  21 , and the phase of the electric current with respect to the voltage applied on the second electrode  22 . For example, when the phase of the electric current with respect to the voltage applied on the first electrode  21  and the phase of the electric current with respect to the voltage applied on the second electrode  22  differ, it can be considered that there is an abnormality such as a burn-out between the first electrode  21  and the second electrode  22 . 
     As described above, when the seating surface  101   a  of the seat  101  is wet or when the material comprising the seat  101  is tinged with moisture, the capacitance between the first electrode  21  and second electrode  22  and the body  100  increases. The difference between the phase of the electric current with respect to the voltage applied on the first electrode  21  and the phase of the electric current with respect to the voltage applied on the second electrode  22  may be compared between after the passage of electric current to the heating elements  23  and  24  is accomplished and before the passage of electric current to the heating elements  23  and  24  is accomplished, taking this into consideration. 
     In addition, with the above-described preferred embodiment the voltage V between the first electrode  21  and second electrode  22  and the body  100  and the electric current i supplied to the first electrode  21  and the second electrode  22  were monitored and detection of the occupant  120  seated on the seat  101  was accomplished based on the in-phase component I of the electric current i with respect to the voltage V and the quadrature component Q of the electric current i with respect to the voltage V. This is not intended to be limiting, for a voltage partitioning method may be used, for example to find the quadrature component Q, and detection of the occupant  120  seated on the seat  101  may be accomplished based on the quadrature component Q. 
     The detection unit according to the above-explained embodiments may be configured by hardware resources, or may be a computer or a microcomputer configured by a CPU (Central Processing Unit), a main memory, and an auxiliary memory. 
     Various embodiments and modifications are available to the present invention without departing from the broad sense of spirit and scope of the present invention. The above-described embodiments are given for explaining the present invention and do not confine the scope of the present invention. In other words, the scope of the present invention is set forth by the scope of claims, not by the embodiments. Various modifications made within the scope of claims and scope of significance of the invention equivalent thereto are considered to fall under the scope of the present invention. 
     The heating system of the present invention is suitable for the detection of the occupant seated on the seat.