Sensor system, seat, and sensor unit

Abstract

To provide a technology capable of enhancing the received power of a power receiving antenna circuit.SOLUTION: A sensor system has a power supply device having a power transmission antenna disposed within a vehicle, a cushion body made of dielectric material constituting a part of a seat disposed within the vehicle, a sensor provided on the seat, and a power receiving antenna circuit disposed inside the cushion body, which receives power transmitted from the power transmission antenna and outputs power supplied to the sensor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a sensor system, a seat, and a sensor unit. [Background technology]

[0002] BACKGROUND ART In recent years, in vehicles such as passenger cars, sensors that detect conditions inside the vehicle, such as the temperature inside the vehicle, are sometimes installed in order to improve the interior comfort of the vehicle. To supply power to such sensors via a wired connection would require complicated wiring, which could lead to increased costs and weight. To address this issue, wireless power supply to sensors has been considered. For example, Patent Document 1 discloses a technology relating to a wireless power feeding system that transmits power by radio waves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2011-525098 Summary of the Invention [Problem to be solved by the invention]

[0004] When wirelessly feeding power to a sensor, a power receiving antenna circuit is required to receive the transmitted power and provide the power to the sensor. The size of the antenna element in this receiving antenna circuit depends on the wavelength of the radio waves to be received. The frequency of radio waves transmitted wirelessly ranges from 920 GHz to several GHz. The length of the antenna element for receiving these radio waves can be approximately 150 mm. Furthermore, the placement of the antenna element can be limited by the position of the transmitting antenna. Considering that the interior of a vehicle is relatively small and has limited placement, it may be difficult to properly place the antenna elements within the vehicle.

[0005] Here, it is possible to reduce the length of the antenna element and make the power receiving antenna circuit smaller. In this case, however, the antenna element becomes omnidirectional, resulting in a problem of reduced received power. Therefore, an object of the present disclosure is to provide a technique that can increase the received power of a power receiving antenna circuit. [Means for solving the problem]

[0006] The sensor system of the embodiment includes a power supply device having a power transmitting antenna arranged inside a vehicle, a cushion body made of a dielectric material that forms part of a seat arranged inside the vehicle, a sensor provided on the seat, and a power receiving antenna circuit arranged inside the cushion body that receives transmitted power from the power transmitting antenna and outputs power that is provided to the sensor. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to increase the received power of a power receiving antenna circuit. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a side view showing an example of a vehicle equipped with a sensor system according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the relationship between the sensor system and each part of the vehicle. [Figure 3] FIG. 3 is a block diagram showing an example of the configuration of the sensor unit. [Figure 4] FIG. 4 is a perspective view of the headrest according to the first embodiment. [Figure 5] FIG. 5 is a cross-sectional view of the headrest. [Figure 6A] FIG. 6A is a cross-sectional view of the sensor unit. [Figure 6B] FIG. 6B is a diagram of the sensor unit with the lid removed, viewed from the X1 direction. [Figure 7] FIG. 7 is a cross-sectional view of a sensor unit according to a modified example. [Figure 8] FIG. 8 is a perspective view of a sensor unit according to another modified example. [Figure 9] FIG. 9 is a cross-sectional view of a headrest according to the second embodiment. [Figure 10] FIG. 10 is a diagram for explaining the position of the rectenna relative to the headrest. [Figure 11A] FIG. 11A is a graph showing the change in the gain of the rectenna when the distance L is changed. [Figure 11B] FIG. 11B is a graph showing the change in gain of the rectenna when the width W is changed. [Figure 12] FIG. 12 is a diagram for explaining the thickness of the insulating layer in the cushion body model. [Figure 13] FIG. 13 is a graph showing the change in the gain of the rectenna when the thickness of the insulating layer is changed. [Figure 14A] FIG. 14A is a graph showing the directional characteristics of Comparative Example 1. As shown in FIG. [Figure 14B] FIG. 14B is a graph showing the directional characteristics of the first embodiment. [Figure 15] FIG. 15 is a cross-sectional view of a headrest according to Comparative Example 2. As shown in FIG. [Figure 16A] FIG. 16A is a graph showing the directional characteristics of Comparative Example 2. As shown in FIG. [Figure 16B] FIG. 16B is a graph showing the directional characteristics of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] First, the contents of the embodiment will be listed and explained. [Outline of the embodiment]

[0010] (1) A sensor system according to an embodiment of the present disclosure includes a power supply device having a power transmitting antenna disposed within a vehicle, a cushion body made of a dielectric material that forms part of a seat disposed within the vehicle, a sensor provided on the seat, and a power receiving antenna circuit disposed within the cushion body that receives power transmitted from the power transmitting antenna and outputs power to be provided to the sensor.

[0011] According to the above configuration, the power receiving antenna circuit is disposed inside the cushion body, and therefore receives radio waves that are radiated from the power transmitting antenna and pass through the cushion body. The cushion, which forms part of the seat, has a convex curved surface as a whole and is made of a dielectric material. Therefore, radio waves incident on the cushion are refracted so that they are concentrated toward the inside of the cushion. In other words, the cushion functions like a dielectric lens. This allows the position of the power receiving antenna circuit inside the cushion body to be appropriately set so that the gain of the radio waves that pass through the cushion body and reach the cushion body is increased, thereby increasing the received power of the power receiving antenna circuit. The sensor system may further include a transmitter that wirelessly transmits the output of the sensor, and by including the transmitter, the output of the sensor can be output to the outside.

[0012] (2) In the sensor system of (1) above, the cushion body may have a main body and an internal space provided inside the main body and accommodating the power receiving antenna circuit. In this case, the power receiving antenna circuit can be easily disposed inside the cushion body.

[0013] (3) In the sensor system of (2) above, when the main body has a first surface on the side of the power transmitting antenna and a second surface opposite the first surface, the internal space may be provided closer to the second surface. In this case, by providing the internal space closer to the second surface, the thickness of the main body of the cushion body interposed between the power transmitting antenna and the power receiving antenna circuit is increased, which results in more effective increase in the received power of the power receiving antenna circuit.

[0014] (4) In the sensor system of (2) or (3) above, an insulating layer having a dielectric tangent lower than that of the dielectric material may be further provided between the inner surface of the internal space and the outer surface of the receiving antenna circuit. In this case, by providing an insulating layer, it is possible to reduce power loss due to the dielectric loss tangent of the cushion body.

[0015] (5) In the sensor system of (4) above, when the wavelength of the radio wave radiated from the power transmitting antenna is λ, the thickness of the insulating layer may be 0.01λ or more and 0.04λ or less. If the thickness of the insulating layer is less than 0.02λ, the power loss due to the cushion becomes relatively large, resulting in a decrease in the received power of the power receiving antenna circuit.If the thickness of the insulating layer is more than 0.05λ, the effect of reducing power loss due to the cushion becomes saturated, and the insulating layer becomes unnecessarily thick. By setting the thickness of the insulating layer to 0.02λ or more and 0.05λ or less, it is possible to effectively reduce the power loss caused by the cushion body.

[0016] (6) In the sensor system of (4) or (5) above, the insulating layer may include a polystyrene foam layer. In this case, an insulating layer can be provided by interposing polystyrene foam between the wall of the internal space and the power receiving antenna circuit.

[0017] (7) In the sensor system of (4) or (5), the insulating layer may include an air layer. In this case, if a gap is provided between the inner surface of the internal space and the power receiving antenna circuit, an insulating layer can be provided.

[0018] (8) Furthermore, in any one of the sensor systems (4) to (7) above, the sensor system may further include a resin case housed in the internal space and defining the insulating layer by housing the receiving antenna circuit therein. In this case, by housing the power receiving antenna circuit in the resin case, an insulating layer can be easily provided between the inner surface of the internal space and the power receiving antenna circuit.

[0019] (9) Furthermore, in the sensor system of (1) above, when the power receiving antenna circuit has an antenna element and an antenna substrate on which the antenna element is mounted, the antenna substrate may be a flexible substrate. In this case, the antenna substrate can be deformed according to the shape of the cushion body, and therefore, the antenna substrate deformed so as to increase the received power of the power receiving antenna circuit can be placed inside the cushion body.

[0020] (10) In the sensor system of any one of (1) to (9) above, the portion of the seat may include a headrest. In this case, if the power transmitting antenna is disposed on the ceiling side inside the vehicle, the power receiving antenna circuit and the power transmitting antenna can be disposed close to each other.

[0021] (11) Another embodiment is a seat disposed in a vehicle, the seat including a sensor, a cushion body made of a dielectric material, and a power receiving antenna circuit disposed inside the cushion body, receiving transmitted power from a power transmitting antenna disposed in the vehicle, and outputting power to be provided to the sensor.

[0022] (12) Another embodiment is a sensor unit provided in a seat arranged in a vehicle, the sensor unit including a sensor, a power receiving antenna circuit that receives transmitted power from a power transmitting antenna arranged in the vehicle and outputs power to be provided to the sensor, and a resin case that has an internal storage space for storing the power receiving antenna circuit and is arranged inside a cushion made of a dielectric material that constitutes part of the seat.

[0023] According to the above configuration, the resin case that houses the power receiving antenna circuit and is placed inside the cushion body is provided, so that the power receiving antenna circuit can be placed inside the cushion body made of a dielectric material. This makes it possible to increase the received power of the power receiving antenna circuit.

[0024] (13) In the sensor unit of (12) above, if the receiving antenna circuit has an antenna board, the sensor unit may further include a support member that is provided on the inner surface of the storage space and supports the antenna board at a position where a predetermined gap is provided between the antenna board and the inner surface. In this case, an insulating layer including an air layer can be provided between the antenna substrate and the resin case, thereby reducing the power loss caused by the cushion body.

[0025] (14) In the sensor unit of (13) above, the support member may further include a circuit board accommodated in the accommodation space, a support provided on the inner surface of the resin case for supporting the circuit board against the inner surface, and a wire for electrically connecting the antenna board and the circuit board. In this case, the antenna substrate can be supported by the circuit board, the support posts, and the wires.

[0026] (15) The sensor unit of (12) above may further include a line that physically connects the sensor to the resin case that is separate from the sensor and supplies power from the resin case to the sensor. In this case, the sensor and the resin case are separate bodies separated by a line, so the power receiving antenna circuit can be disposed inside the cushion body, while the sensor can be disposed outside the cushion body.

[0027] [Details of the embodiment] Preferred embodiments will now be described with reference to the drawings. At least some of the embodiments described below may be combined in any manner. [Overall structure] Fig. 1 is a side view showing an example of a vehicle equipped with a sensor system according to an embodiment, with a part of the vehicle 1 cut away to show the interior of a vehicle compartment 1a. In FIG. 1, a vehicle 1 is a vehicle (passenger car) including an electric vehicle, an internal combustion engine vehicle, a hybrid vehicle, and the like.

[0028] The sensor system 4 provided in the vehicle 1 is a system that detects the state inside the vehicle compartment 1a using sensors arranged inside the vehicle compartment 1a. The sensor system 4 includes a power supply device 6 and a plurality of sensor units 8. The sensor system 4 may include only one sensor unit 8. When the sensor system 4 includes a plurality of sensor units 8, the sensor units 8 can be arranged at a plurality of locations within the vehicle interior 1a. The power supply device 6 is installed on the ceiling surface 1a1 inside the vehicle interior 1a. The power supply device 6 has a power transmission antenna 6a. The power supply device 6 wirelessly supplies power to the multiple sensor units 8 by emitting power supply radio waves from the power transmission antenna 6a inside the vehicle interior 1a.

[0029] Each of the plurality of sensor units 8 includes a sensor that detects the state inside the vehicle interior 1a. The sensor unit 8 has a function of wirelessly transmitting output information that indicates the output of the sensor. The sensor unit 8 also has the function of receiving radio waves for power supply from the power supply device 6 and converting the radio waves into electric power. The sensor unit 8 is configured to operate using the electric power supplied from the power supply device 6. Therefore, the sensor unit 8 can be powered and operated without being connected to another external device by wire. The configuration of the sensor unit 8 will be described in detail later.

[0030] The plurality of sensor units 8 are provided at the plurality of seats 10 in the vehicle interior 1a. Each of the plurality of seats 10 has a seat portion 11 including a seat portion and a backrest portion, and a headrest 12. In this embodiment, the sensor unit 8 is provided in the headrest 12. The headrest 12 has the sensor unit 8 built in. In other words, the headrest 12 can also be said to be a sensor in the sensor system 4.

[0031] The vehicle 1 includes a power source 14 and an ECU (Electronic Control Unit) 16 . Power supply 14 is, for example, a secondary battery, and includes a lead-acid battery, a lithium-ion battery, a nickel-metal hydride battery, etc., as well as a capacitor, etc. Power supply 14 is a source of power supply to power feeding device 6. Power supply 14 is also a source of power supplied to each part of vehicle 1. Power supply 14 may also store power generated by an alternator or a motor. The ECU 16 has a function of performing processes related to the control of each part of the vehicle 1. The processes include processes that use output information from the sensor unit 8, as will be described later.

[0032] FIG. 2 is a diagram showing the relationship between the sensor system 4 and each part of the vehicle 1. As shown in FIG. 2, the power supply 14 is connected to the power supply device 6. The power supply device 6 is supplied with power from the power supply 14. The power supply device 6 generates a power supply signal based on the power supplied from the power supply 14 and supplies the signal to the power transmitting antenna 6a. The power transmitting antenna 6a emits the power supply signal as a power supply radio wave and transmits it to the plurality of sensor units 8.

[0033] The sensor units 8 detect the state inside the vehicle interior 1a using the power obtained by receiving the power supply radio waves and wirelessly transmit output information indicating the output of the sensors. The sensor units 8 receive the power supply radio waves inside the headrest 12.

[0034] The vehicle 1 further includes a receiver 18. The receiver 18 is disposed in the vehicle interior 1a. The receiver 18 receives output information transmitted from the plurality of sensor units 8 and provides the output information to the ECU 16. When the output information is given to the ECU 16, the ECU 16 controls the state inside the vehicle compartment 1a based on the output information. For example, the ECU 16 controls the air conditioner installed in the vehicle 1 based on the output information.

[0035] FIG. 3 is a block diagram showing an example of the configuration of the sensor unit 8. As shown in FIG. 3, the sensor unit 8 includes a rectenna 20, a power control circuit 22, a sensor 24, and a transmitter .

[0036] The rectenna 20 has a power receiving antenna 20a and a rectifier circuit 20b. The power receiving antenna 20a receives radio waves for power supply from the power supply device 6. The power receiving antenna 20a provides an electrical signal based on the received radio waves to the rectifier circuit 20b. The rectifier circuit 20b rectifies the electrical signal provided by the power receiving antenna 20a, converts it into DC power, and outputs the converted DC power. In other words, the rectenna 20 constitutes a power receiving antenna circuit that receives the transmitted power from the power transmitting antenna 6a and outputs the power. The DC power output from the rectifier circuit 20b is supplied to the power control circuit 22.

[0037] Power control circuit 22 has the function of converting the DC power provided by rectenna 20 to a predetermined voltage and providing the converted power to sensor 24 and transmitter 26. Power control circuit 22 also has the function of storing or discharging the DC power provided by rectenna 20 and controlling the power provided to sensor 24 and transmitter 26. Power control circuit 22 may provide power to sensor 24 and transmitter 26 continuously, or may provide power to sensor 24 and transmitter 26 periodically.

[0038] As described above, the sensor 24 is a sensor for detecting the state inside the vehicle compartment 1a. More specifically, the sensor 24 includes a temperature sensor, a humidity sensor, an acceleration sensor, an illuminance sensor, etc. The sensor 24 has a function of detecting the state inside the vehicle compartment 1a, such as the temperature, humidity, acceleration (vibration), and illuminance. When DC power is supplied from the power control circuit 22, the sensor 24 provides an output indicating the result of detecting the state inside the vehicle compartment 1a to the transmitter 26.

[0039] The transmitter 26 has a transmission antenna 26a and has a function of performing wireless communication with the receiver 18 on the vehicle 1 side via the transmission antenna 26a. The transmitter 26 wirelessly transmits the output provided by the sensor 24 as output information. When DC power is provided from the power control circuit 22, the transmitter 26 establishes a communication connection with the receiver 18 and starts wireless transmission of the output information.

[0040] For example, when a main switch of the vehicle 1 is turned on, the power supply device 6 starts wirelessly supplying power to the plurality of sensor units 8. As a result, the multiple sensor units 8 receive power transmitted from the power supply device 6. When power is supplied from the power supply device 6, the sensors 24 of each of the multiple sensor units 8 start detecting the condition inside the vehicle interior 1a and outputting the detection results. Furthermore, the transmitter 26 establishes a communication connection with the receiver 18 and starts wirelessly transmitting output information. Note that when DC power is supplied, the transmitter 26 starts wirelessly transmitting the output information, and may continue transmitting while power is being supplied.

[0041] The output information transmitted by the transmitter 26 is received by the receiver 18 and provided to the ECU 16 . The ECU 16 receives the output information, acquires information indicating the state inside the vehicle compartment 1a from the output information, and performs control related to the state inside the vehicle compartment 1a based on the acquired information indicating the state inside the vehicle compartment 1a.

[0042] [Regarding the headrest 12 according to the first embodiment] FIG. 4 is a perspective view of the headrest 12 according to the first embodiment. In the following description, the three mutually orthogonal directions in each drawing are referred to as the X direction, Y direction, and Z direction. Also, as shown in FIG. 1, one of the X directions is referred to as the X1 direction, and the opposite direction of the X1 direction is referred to as the X2 direction. One of the Y directions is referred to as the Y1 direction, and the opposite direction of the Y1 direction is referred to as the Y2 direction. One of the Z directions is referred to as the Z1 direction, and the opposite direction of the Z1 direction is referred to as the Z2 direction. The X direction is the front-to-back direction, the Y direction is the left-to-right direction, and the Z direction is the up-down direction. The Z1 direction is the upward direction, the X1 direction is the direction toward the front of the vehicle 1, and the Y1 direction is the direction toward the left when viewed from a passenger facing the front of the vehicle 1.

[0043] The headrest 12 is a rounded, pillow-shaped member. The top surface 12a and bottom surface 12b of the headrest 12 are substantially parallel to the Y direction. The top surface 12a, the front surface 12c on the X1 side, the rear surface 12d on the X2 side, the left surface 12e on the Y1 side, and the right surface 12f on the Y2 side of the headrest 12 have convex curved surfaces. Note that the convex curved surface referred to here means that the target surface as a whole is a convex curved surface, and even if the outline shape of the cross section between a pair of opposing sides among the four sides defining the target surface is linear, it is sufficient that the outline shape of the cross section between the remaining pair of sides is a convex curved surface. Furthermore, the shape of the headrest 12 is not limited to the shape shown in FIG. 4, as long as it functions as a headrest.

[0044] Fig. 5 is a cross-sectional view of the headrest 12. Fig. 5 shows a cross section parallel to the XZ plane. The contour shape of the cross section of the headrest 12 parallel to the XZ plane has a trapezoidal shape with each side bulging outward by a convex curve. As shown in FIGS. 4 and 5, the headrest 12 includes a sensor unit 8, a frame 28, a cushion body 32, and a cover 34.

[0045] Frame 28 is a gate-shaped member made of steel pipes or the like. Frame 28 has a frame main body 28b disposed inside headrest 12 and a pair of protrusions 28a protruding from undersurface 12b. The pair of protrusions 28a are inserted into the upper end of the backrest of seat portion 11 of seat 10. In this way, headrest 12 is fixed to the upper end of the backrest.

[0046] The cushion body 32 is a member made of, for example, a dielectric material. In this embodiment, polyurethane is used as the dielectric material. The cushion body 32 has elasticity. The cushion body 32 is a buffer member when the occupant's head comes into contact with the headrest 12. The cushion body 32 forms the overall shape of the headrest 12. Therefore, the cushion body 32 is a rounded, pillow-shaped member. The top, front, rear, left, and right surfaces of the cushion body 32 have convex curved surfaces. The cover 34 covers the outer surface of the cushion body 32 .

[0047] As shown in FIG. 5, the cushion body 32 has a main body portion 36, a first internal space 38, and a second internal space 40. The main body 36 is a member made of polyurethane, and constitutes the overall shape of the cushion body 32 . The internal spaces 38 and 40 are spaces provided inside the main body portion 36 .

[0048] The frame main body 28b is housed in the first internal space 38. The first internal space 38 is formed in a shape corresponding to the outer shape of the frame main body 28b. The inner surface of the first internal space 38 abuts against the frame main body 28b. This restricts movement of the frame main body 28b in the first internal space 38. Therefore, the frame main body 28b is held inside the cushion body 32. In other words, the cushion body 32 is held by the frame main body 28b.

[0049] The second internal space 40 accommodates the sensor unit 8. In this embodiment, the sensor unit 8 has one surface parallel to the YZ plane. This surface is a rectangle having long and short sides. Therefore, the sensor unit 8 has a rectangular parallelepiped shape. Therefore, the second internal space 40 is formed in a rectangular parallelepiped shape according to the outer shape of the sensor unit 8. Furthermore, the inner surface 40a of the second internal space 40 abuts against the sensor unit 8. This restricts the movement of the sensor unit 8 within the second internal space 40. Therefore, the sensor unit 8 is held inside the cushion body 32. In this embodiment, the sensor unit 8 is held inside the cushion body 32 with the short sides aligned along the Z direction and the long sides aligned along the Y direction, as shown in FIG. Furthermore, the internal spaces 38, 40 may be spaces formed by hollowing out the material of the main body portion 36, or may be spaces formed by making a slit in the material of the main body portion 36, placing the frame main body 28b and the sensor unit 8 in the slit, and elastically expanding the slit.

[0050] The second internal space 40 is provided closer to the lower surface 36b of the main body 36. The second internal space 40 is also provided below the center of the main body 36 in the up-down direction. Therefore, the sensor unit 8 is held closer to the lower surface 36b inside the main body 36. Furthermore, the sensor unit 8 is held lower than the center in the up-down direction inside the main body 36.

[0051] [About Sensor Unit 8] Fig. 6A is a cross-sectional view of the sensor unit 8. Fig. 6A shows a cross section parallel to the XY plane when the sensor unit 8 is placed in the headrest 12. That is, Fig. 6A explains each part of the sensor unit 8 based on each direction when a circuit board 44, a bottom surface 46a1, etc., which will be described later, are placed along the YZ plane.

[0052] As shown in FIG. 6A, the sensor unit 8 includes a circuit board 44 and a resin case 46 in addition to the rectenna 20. The resin case 46 is a rectangular parallelepiped member made of ABS resin, POM resin, polystyrene foam, or the like. The resin case 46 includes a case body 46a and a lid 46b. The resin case 46 forms the outer shape of the sensor unit 8. Therefore, when the sensor unit 8 is housed in the second internal space 40, the resin case 46 comes into contact with the inner surface 40a of the second internal space 40. The rectenna 20 and the circuit board 44 are housed inside the resin case 46. In other words, the space inside the resin case 46 is a housing space that houses the rectenna 20 and the circuit board 44.

[0053] The circuit board 44 is a rigid board on which the above-described power control circuit 22, sensor 24, and transmitter 26 are mounted. The circuit board 44 has a rectangular plate shape. The circuit board 44 is fixed to the bottom surface 46a1 by support posts 48. The bottom surface 46a1 is an inner surface of the case body 46a and faces the X1 direction. The bottom surface 46a1 has a rectangular shape. The bottom surface 46a1 is aligned along the YZ plane. The support pillars 48 are provided so as to protrude from the bottom surface 46a1 of the case body 46a. The support pillars 48 support the circuit board 44 against the bottom surface 46a1. At this time, the circuit board 44 is supported so as to be aligned along the YZ plane. A predetermined gap is provided between the case body 46a (bottom surface 46a1) and the circuit board 44. A predetermined gap is also provided between the circuit board 44 and a cover surface 46b1 of the cover 46b. The cover surface 46b1 is the inner surface of the cover 46b and faces in the X2 direction. The cover surface 46b1 has a rectangular shape. The cover surface 46b1 is aligned along the YZ plane.

[0054] FIG. 6B is a diagram of the sensor unit 8 with the cover 46b removed, viewed from the X1 direction. As shown in FIG. 6B, the rectenna 20 includes an antenna substrate 50, a power receiving antenna 20a, and a circuit chip 52. The circuit chip 52 is a circuit chip including the rectifier circuit 20b. The antenna substrate 50 is a rectangular rigid substrate and is disposed along the YZ plane. The power receiving antenna 20a and the circuit chip 52 are mounted on a first surface 50a of the antenna substrate 50. The first surface 50a is the surface of the antenna substrate 50 on the lid 46b side, and faces in the X1 direction.

[0055] The power receiving antenna 20a includes an antenna element 20a1 and a pair of lines 20a2. The antenna element 20a1 and the pair of lines 20a2 are made of metal foil such as copper foil patterned on the first surface 50a. The antenna element 20a1 has a C-shaped loop shape, so the power receiving antenna 20a of this embodiment forms a loop antenna. When the sensor unit 8 is disposed inside the headrest 12, the center C of the antenna element 20a1 is located at the center in the Y direction of the headrest 12. As a result, the antenna element 20a1 is disposed at the center of the headrest 12 in the Y direction. A pair of lines 20a2 connects both ends of the antenna element 20a1 to the circuit chip 52.

[0056] The power receiving antenna 20a of the rectenna 20 of this embodiment is a relatively small, high-impedance loop antenna. The impedance of the power receiving antenna 20a is designed to match that of the rectifier circuit 20b. In this way, the rectenna 20 of this embodiment is made compact by employing a small, high-impedance loop antenna. For example, the diameter of antenna element 20a1 of rectenna 20 of this embodiment is several tens of mm. However, since antenna element 20a1 is small, rectenna 20 is omnidirectional.

[0057] The circuit chip 52 is connected to the power control circuit 22 mounted on the circuit board 44 . The antenna board 50 and the circuit board 44 are electrically connected by a pair of wires 54 . A pair of wires 54 connects the circuit chip 52 to the power control circuit 22 on the circuit board 44 .

[0058] Ends of the pair of wires 54 on the antenna substrate 50 side are fixed to an edge on the Y1 direction side of the first surface 50a of the antenna substrate 50. Ends of the pair of wires 54 on the circuit board 44 side are fixed to an edge on the Y2 direction side of the board surface 44a of the circuit board 44. In this way, the pair of wires 54 connect the edge of the antenna substrate 50 and the edge of the circuit board 44.

[0059] Furthermore, the pair of wires 54 supports the antenna substrate 50 so that the antenna substrate 50 does not come into contact with the resin case 46 . That is, the circuit board 44, the support posts 48, and the pair of wires 54 constitute the support member 47. The support member 47 is a member that supports the antenna board 50 so that the antenna board 50 does not come into contact with the resin case 46. The support member 47 provides a predetermined gap between the first surface 50a of the antenna board 50 and the cover surface 46b1. A predetermined gap is also provided between the second surface 50b of the antenna board 50 and the bottom surface 46a1. The second surface 50b is the surface of the antenna board 50 on the case main body 46a side, and faces in the X2 direction.

[0060] As a result, an insulating layer 56 (FIG. 6A) is provided between the rectenna 20 (power receiving antenna circuit) and the inner surface 40a of the second internal space 40. This insulating layer 56 is an air layer. In this manner, the resin case 46 is housed in the second internal space 40 and defines the insulating layer 56 by housing the rectenna 20 therein. Since the system 4 of this embodiment includes the resin case 46, by housing the rectenna 20 in the resin case 46, the insulating layer 56 can be easily provided between the inner surface 40a of the second internal space 40 and the rectenna 20.

[0061] As described above, the insulating layer 56 is an air layer, and therefore has a lower dielectric tangent than polyurethane, which is the material of the cushion body 32. Therefore, for example, compared to when the rectenna 20 and the main body 36 of the cushion body 32 are in direct contact, the loss of received power of the rectenna 20 caused by the dielectric tangent of the cushion body 32 can be reduced.

[0062] Furthermore, when the wavelength of the radio waves emitted from the power transmitting antenna 6a is λ, the thickness t of the insulating layer 56 may be set to be 0.02λ or more and 0.05λ or less. The thickness t includes a thickness t1 between the first surface 50a and the cover surface 46b1, and a thickness t2 between the second surface 50b and the bottom surface 46a1. The insulating layer 56 is present at least on the outer surfaces (the first surface 50a and the second surface 50b) of the antenna substrate 50. If thickness t is less than 0.02λ, the power loss due to cushion body 32 becomes relatively large, resulting in a decrease in the received power of rectenna 20. If thickness t is greater than 0.05λ, the effect of cushion body 32 in reducing power loss becomes saturated, and resin case 46 becomes unnecessarily thick, making it difficult to properly position it within headrest 12. Setting the thickness t to be equal to or greater than 0.02λ and equal to or less than 0.05λ effectively reduces the power loss caused by the cushion body 32. Furthermore, the resin case 46 can be made relatively compact, making it easier to appropriately arrange it within the headrest 12.

[0063] According to the above configuration, the rectenna 20 (power receiving antenna circuit) is disposed inside the cushion body 32. Therefore, the rectenna 20 receives radio waves that are radiated from the power transmitting antenna 6a and pass through the cushion body 32. Here, the surface of the cushion body 32 of the headrest 12 is a convex curved surface as a whole, and the cushion body 32 is made of a dielectric material. Therefore, radio waves incident on the cushion body 32 are refracted so as to be concentrated toward the inside of the cushion body 32. In other words, the cushion body 32 functions like a dielectric lens. This allows the reception power of the rectenna 20 to be increased by appropriately setting the position of the rectenna 20 inside the cushion body 32 so that the gain of the radio waves that pass through and reach the cushion body 32 is increased.

[0064] Furthermore, with the above configuration, the received power of rectenna 20 can be increased, which makes it possible to reduce the power transmitted by power feeding device 6 and improve the power consumption of vehicle 1 equipped with this system 4. Furthermore, interference with wireless communication systems other than this system 4 can be reduced.

[0065] Furthermore, since the cushion body 32 of this embodiment has the main body portion 36 and the second internal space 40, the sensor unit 8 including the rectenna 20 can be easily disposed inside the cushion body 32.

[0066] In this embodiment, the power transmitting antenna 6a is provided directly above the headrest 12 on the ceiling surface 1a1. Therefore, the upper surface 36a (first surface) of the main body 36 is located on the power transmitting antenna 6a side. The lower surface 36b (second surface) of the main body 36 faces the upper surface 36a. The second internal space 40 is provided closer to the lower surface 36b than to the upper surface 36a. This ensures a greater thickness of the main body 36 interposed between the power transmitting antenna 6a and the rectenna 20. As a result, the received power of the rectenna 20 can be increased more effectively. Furthermore, since the cushion body 32 of this embodiment constitutes the headrest 12, which is part of the seat 10, the rectenna 20 and the power transmitting antenna 6a can be disposed close to each other.

[0067] In this embodiment, the insulating layer 56 is an air layer. However, the insulating layer 56 may have a dielectric loss tangent lower than that of polyurethane, which is the material of the cushion body 32. Therefore, the insulating layer 56 may be, for example, a polystyrene foam layer. A polystyrene foam layer has a dielectric loss tangent lower than that of polyurethane. Therefore, even when the insulating layer 56 is a polystyrene foam layer, the loss of received power of the rectenna 20 caused by the dielectric loss tangent of the cushion body 32 can be reduced.

[0068] When the insulating layer 56 is a polystyrene foam layer, the insulating layer 56 can be made up of a first member 56a and a second member 56b, as shown in FIG. The first member 56a and the second member 56b are members made of polystyrene foam. The first member 56a is disposed on the X2 side of the rectenna 20 and abuts against the second surface 50b of the antenna substrate 50. The second member 56b is disposed on the X1 side of the rectenna 20 and abuts against the first surface 50a of the antenna substrate 50. The rectenna 20 and the circuit board 44 are sandwiched and held between a first member 56a and a second member 56b.

[0069] In this case, insulating layer 56 contacts inner surface 40a of second internal space 40 and rectenna 20. Therefore, sensor unit 8 having insulating layer 56 can be configured without using resin case 46. By omitting resin case 46 in this way, the configuration of sensor unit 8 can be simplified.

[0070] In addition, the case where resin case of sensor unit 8 of this embodiment houses rectenna 20 and sensor 24 has been exemplified. However, sensor 24 may be provided outside resin case . 8, sensor unit 8 may include line 60 connecting sensor 24 and resin case 46. Resin case 46 houses rectenna 20 and circuit board 44. Power control circuit 22 and transmitter 26, other than sensor 24, are mounted on circuit board 44. Line 60 is a line for supplying power from resin case 46 to sensor 24 and for providing the output of sensor 24 to resin case 46.

[0071] In this case, the sensor 24 and the resin case 46 are separate bodies. The sensor 24 and the resin case 46 are physically connected via the line 60. Therefore, the rectenna 20 can be disposed inside the cushion body 32, while the sensor 24 can be disposed outside the cushion body 32. This allows the sensor 24 to be disposed in an environment more suitable for detecting the state inside the vehicle interior 1a, thereby improving the accuracy of the sensor 24.

[0072] [Regarding the headrest 12 according to the second embodiment] FIG. 9 is a cross-sectional view of a headrest 12 according to the second embodiment. This embodiment differs from the first embodiment in that the antenna substrate 50 included in the rectenna 20 is an FPC (Flexible Printed Circuits) and the rectenna 20 is curved. Additionally, the sensor unit 8 of this embodiment includes a resin case 62 that houses the circuit board 44, and differs from the first embodiment in that the rectenna 20 and the resin case 62 containing the circuit board 44 are separate bodies.

[0073] The second internal space 40 of this embodiment is provided closer to the upper surface 36a of the main body portion 36. The second internal space 40 is curved so as to fit the shape of the upper surface 36a. Therefore, the rectenna 20 is held close to the upper surface 36a inside the main body 36. The rectenna 20 is also held above the frame main body 28b (frame 28). Furthermore, the antenna substrate 50 of the rectenna 20 is curved to fit the shape of the upper surface 36a in accordance with the shape of the second internal space 40.

[0074] An insulating layer 56 is provided between the rectenna 20 and the inner surface 40a of the second internal space 40. The insulating layer 56 is a polystyrene foam layer. The insulating layer 56 is composed of a first member 56a and a second member 56b, both made of polystyrene foam. The rectenna 20 is sandwiched and held between the first member 56a and the second member 56b. The first member 56a and the second member 56b are curved to follow the shape of the upper surface 36a in accordance with the shape of the second internal space 40. Therefore, the first member 56a and the second member 56b hold the antenna substrate 50 while bending the antenna substrate 50.

[0075] As described above, the sensor unit 8 of this embodiment includes the resin case 62 that houses the circuit board 44. The resin case 62 is housed in the third internal space 41. The third internal space 41 is a space provided on the rear surface 36d side of the main body 36. The third internal space 41 is exposed at the rear surface 36d. Therefore, the resin case 62 housed in the third internal space 41 is also exposed. This allows the sensor 24 mounted on the circuit board 44 to be placed in an environment more suitable for detecting the condition inside the vehicle interior 1a. As a result, the accuracy of the sensor 24 is improved.

[0076] Resin case 62 and rectenna 20 are connected by lines 64. DC power output by rectenna 20 is applied via lines 64 to each component mounted on circuit board 44.

[0077] In this embodiment, since the antenna substrate 50 is an FPC, it is possible to deform the antenna substrate 50 according to the shape of the cushion body 32 (main body portion 36). Therefore, the antenna substrate 50 that has been deformed so as to increase the received power of the rectenna 20 can be placed inside the cushion body 32. Furthermore, in this embodiment, the rectenna 20 is held closer to the upper surface 36a of the main body 36, so that it can be disposed closer to the power transmitting antenna 6a.

[0078] 〔others〕 In the above embodiments, the sensor unit 8 is provided only in the headrest 12 of the seat 10, but the sensor unit 8 may be provided inside a cushion that constitutes part of the seat 10. More specifically, the sensor unit 8 may be provided in the seat portion or backrest portion of the seat 10, which is included in the seat portion 11 that has a cushion made of a dielectric material.

[0079] Furthermore, in each of the above embodiments, examples have been given of sensor units 8 being provided near the top and bottom of cushion body 32, but sensor unit 8 may simply be disposed within main body portion 36 of cushion body 32, thereby increasing the reception power of rectenna 20. Furthermore, in the above-described embodiments, the main body 36 of the cushion body 32 is formed from polyurethane, but a dielectric material other than polyurethane may also be used.

[0080] In the first embodiment described above, the antenna substrate 50 of the rectenna 20 is arranged along the YZ plane, but the antenna substrate 50 may be arranged along the XY plane or the XZ plane. In this case, too, the received power of the rectenna 20 can be increased, as in the first embodiment. Furthermore, in each of the above embodiments, the power receiving antenna 20a of the rectenna 20 is configured as a loop antenna, but the power receiving antenna 20a may be another antenna such as a dipole antenna or a planar antenna.

[0081] [About verification testing] Next, a verification test conducted to examine the effects of this system 4 will be described. As a test method, a model of the headrest 12 and rectenna 20 provided in the present system 4 was constructed, and the evaluation target values ​​were calculated and evaluated by computer simulation. The details of the four tests that were carried out are described below. Test 1: Verification of the optimal position of the rectenna 20 relative to the headrest 12 Test 2: Verification of the thickness of the insulating layer 56 Test 3: Evaluation of the directional characteristics of the rectenna 20 according to the first embodiment Test 4: Evaluation of the directional characteristics of the rectenna 20 according to the second embodiment

[0082] [About Test 1] In Test 1, a model of headrest 12 according to the first embodiment was used to determine the change in gain of rectenna 20 when the relative position of rectenna 20 with respect to headrest 12 was changed. In Test 1, the gain was determined when power was supplied by radio waves with a frequency of 920 MHz. The power transmitting antenna 6a was positioned directly above the headrest 12 in the Z direction.

[0083] Fig. 10 is a diagram illustrating the position of rectenna 20 relative to headrest 12. In Fig. 10, distance L is the distance in the Z direction from upper surface 12a (upper surface 36a) to center C of antenna element 20a1. Width W is the dimension of headrest 12 (cushion body 32) in the Y direction. Note that diameter D of antenna element 20a1 of rectenna 20 is set to 40 mm, and the maximum dimension of headrest 12 in the X direction is 30 mm.

[0084] In Test 1, the change in gain of rectenna 20 when the distance L and width W were changed was obtained by simulation. When the distance L was changed, the width W was set to 150 mm. The position of rectenna 20 in the X direction was set as follows: First, rectenna 20 was placed at the center of headrest 12 in the X direction, and the distance L at which the gain of rectenna 20 was maximized was determined. After that, distance L was fixed, and the position in the X direction of rectenna 20 at which the gain of rectenna 20 was maximized was determined. This determined position was used as the reference position of rectenna 20 in the X direction, and the distance L and width W were changed. When the width W was changed, the distance L was set to 130 mm.

[0085] Fig. 11A is a graph showing the change in gain of rectenna 20 when distance L is changed. In Fig. 11A, the horizontal axis represents distance L, and the vertical axis represents gain. 11A, graph g1 shows the change in gain of the Y-direction component in the Z-axis direction. Graph g2 shows the change in gain of the X-direction component in the Z-axis direction. Graph g3 shows the gain of rectenna 20 when there is no cushion body 32 around it. The position of rectenna 20 when there is no cushion body 32 around it is the same as the position of rectenna 20 arranged inside headrest 12 of the first embodiment.

[0086] As shown in FIG. 11A, if the distance L is 80 mm or more, the gain in the Y direction is higher than the gain of the rectenna 20 alone. Furthermore, when the distance L is less than 130 mm, the gain in the X direction is lower than the gain in the case of rectenna 20 alone. However, when the distance L is greater than 130 mm, the gain in the X direction is higher than the gain in the case of the rectenna 20 alone.

[0087] Fig. 11B is a graph showing the change in gain of rectenna 20 when width W is changed. In Fig. 11B, the horizontal axis represents width W, and the vertical axis represents gain. 11B, graph g4 shows the change in gain in the Y direction, graph g5 shows the change in gain in the X direction, and graph g6 shows the gain when rectenna 20 alone is placed in the same position.

[0088] In Test 1, as shown in FIG. 11B, when the width W is 100 mm or more, the gain in the Y direction is higher than the gain in the case of rectenna 20 alone. Furthermore, when the width W is smaller than 150 mm, the gain in the X direction is lower than the gain in the case of rectenna 20 alone. However, when the width W is greater than 150 mm, the gain in the X direction is higher than the gain in the case of the rectenna 20 alone.

[0089] From these, it can be seen that if the rectenna 20 is disposed inside the headrest 12 (cushion body 32), the gain (received power) of the rectenna 20 can be increased. Furthermore, it can be seen that if the distance L is greater than 130 mm, the gain of the rectenna 20 can be further increased. It is also understood that if the width W is greater than 150 mm, the gain of the rectenna 20 can be further increased.

[0090] [Regarding Test 2] In Test 2, a pseudo cushion body model was used to determine the change in gain of rectenna 20 when the thickness t of insulating layer 56 was changed. In Test 2, the thickness t of the portion of insulating layer 56 facing the outer surfaces (first surface 50a and second surface 50b) of antenna substrate 50 was changed.

[0091] FIG. 12 is a diagram for explaining the thickness t of the insulating layer 56 in the cushion body model. Cushion body model R has a main body 100 and an internal space 140. Main body 100 corresponds to main body 36 of headrest 12. Main body 100 has a cubic shape with one side measuring 200 mm. Internal space 140 corresponds to second internal space 40 of headrest 12. Therefore, internal space 140 accommodates rectenna 20. The insulating layer 56 is provided between the rectenna 20 (the antenna substrate 50 thereof) and the inner surface 140a of the internal space 140. In Test 2, the insulating layer 56 was an air layer. In Test 2, the resin case 46 was omitted, and only the insulating layer 56 (air layer) was present between the inner surface 140a and the first surface 50a (second surface 50b) of the antenna substrate 50, as shown in FIG. Here, the frequency of the radio wave for power feeding from the power transmitting antenna 6a was set to 920 MHz.

[0092] Figure 13 is a graph showing the change in gain of rectenna 20 when the thickness t of insulating layer 56 is changed. In Figure 13, the horizontal axis represents the thickness t of insulating layer 56, and the vertical axis represents the gain. The dashed line in Figure 13 indicates the gain level for rectenna 20 alone. The gain for rectenna 20 alone is 1.21.

[0093] As shown in Figure 13, when the thickness t is 0 (when the cushion body 32 and the rectenna 20 are in contact), the gain is 0.25 dBi. However, as the thickness t increases, the gain increases and approaches the gain of the rectenna 20 alone. When the thickness t is 4 mm, the gain is approximately 1 dBi. Furthermore, when the thickness t exceeds 10 mm, the gain becomes sufficiently close to the gain of the rectenna 20 alone. In other words, when the thickness t exceeds 10 mm, the gain becomes saturated. Therefore, it can be said that if the thickness t is 4 mm or more and 10 mm or less, the loss of power received by the rectenna 20 due to the cushion body 32 can be reduced.

[0094] Here, if the wavelength of the power supply radio wave is λ and the thickness is t, the power supply frequency is 920 MHz, so 4 mm is expressed as 0.012λ. Similarly, 10 mm is expressed as 0.04λ. That is, the results of Test 2 show that the power loss caused by the cushion body 32 can be effectively reduced by setting the thickness t to be equal to or greater than 0.01λ and equal to or less than 0.04λ.

[0095] [About Test 3] In Test 3, a model of headrest 12 according to the first embodiment was used, and rectenna 20 (sensor unit 8) with distance L of 35 mm, width W of 180 mm, and thickness t of insulating layer 56 of 2 mm was used as Example 1, while rectenna 20 without surrounding cushion body 32 was used as Comparative Example 1, and the directional characteristics of both were compared. The position of rectenna 20 without surrounding cushion body 32 was the same as the position of rectenna 20 in Example 1.

[0096] Fig. 14A is a graph showing the directional characteristics of Comparative Example 1. Fig. 14B is a graph showing the directional characteristics of Example 1. Arrow Z in Figs. 14A and 14B indicates the Z1 direction, and arrow X indicates the X1 direction. 14A and 14B show the directional characteristics of the polarized wave component along the X direction in the XZ plane (hereinafter also referred to as the X-axis component), and the directional characteristics of the polarized wave component along the Y direction in the XZ plane (hereinafter also referred to as the Y-axis component).

[0097] 14A, graph g7 shows the directional characteristics of the Y-axis component, and graph g8 shows the directional characteristics of the X-axis component. Graph g7 and graph g8 overlap. In FIG. 14B, graph g9 shows the directional characteristics of the Y-axis component, and graph g10 shows the directional characteristics of the X-axis component.

[0098] 14B, the directivity characteristics of Example 1 are improved in the Z1 direction compared to the directivity characteristics of Comparative Example 1. That is, the directivity characteristics of Example 1 are improved in the direction toward the power transmitting antenna 6a. 14B, the gain in the Z1 direction for the X-axis component is improved by about 3 dB compared to the gain (FIG. 14A) of Comparative Example 1. Also, in FIG. 14B, the gain in the Z1 direction for the Y-axis component is improved by about 1 dB compared to the gain of Comparative Example 1.

[0099] From the above results, it can be seen that in the first embodiment, the received power of the rectenna 20 is increased. In addition, as shown in FIG. 14B, it can be seen that the rectenna 20 according to the first embodiment can receive both the X-axis component and the Y-axis component.

[0100] [Regarding Test 4] In Test 4, the rectenna 20 when using the model of the headrest 12 according to the second embodiment was used as Example 2, and the rectenna 20 without a curved shape was used as Comparative Example 2, and the directional characteristics of both were compared.

[0101] Fig. 15 is a cross-sectional view of a headrest 12 according to Comparative Example 2. The sensor unit 8 shown in Fig. 15 differs from the sensor unit 8 of the second embodiment shown in Fig. 9 only in that the rectenna 20 is planar along the XY plane and does not have a curved shape.

[0102] Fig. 16A is a graph showing the directional characteristics of Comparative Example 2. Fig. 16B is a graph showing the directional characteristics of Example 2. Arrow Z in Figs. 16A and 16B indicates the Z1 direction, and arrow X indicates the X1 direction. 16B, the directivity characteristics of Example 2 are improved in the Z1 direction compared to the directivity characteristics of Comparative Example 2. That is, the directivity characteristics of Example 2 are improved in the direction toward the power transmitting antenna 6a. More specifically, in FIG. 16B, the gain in the Z1 direction is improved by about 1 dB compared to the gain of Comparative Example 2 (FIG. 16A). In addition, in FIG. 16B, the gain of Example 2 is improved compared to the gain of Comparative Example 2 (FIG. 16A) in the range of 60 degrees on both sides of the Z1 direction.

[0103] From the above results, it can be seen that in Example 2, the received power of the rectenna 20 can be increased over a wide range in the front-rear direction.

[0104] [Conclusion] It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims, not by the meaning described above, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof. [Explanation of symbols]

[0105] 1 vehicle 1a Cabin 1a1 Ceiling surface 4 Sensor System 6 Power supply equipment 6a Power transmission antenna 8 Sensor Unit 10 seats 11 Seat section 12 Headrest 12a Top side 12b Bottom side 12c front 12d rear 12e left side 12f Right side 14 Power supply 16 ECU 18 Receiver 20 Rectenna (receiving antenna circuit) 20a receiving antenna 20a1 Antenna element 20a2 track 20b rectifier circuit 22 Power control circuit 24 sensors 26 Transmitter 26a Transmitting antenna 28 frames 28a Protrusion 28b frame body 32 Cushion body 34 Cover 36 Main body 36a Top side 36b Bottom side 36d rear 38 1st interior space 40 Second internal space 40a inner surface 41 Third internal space 44 Circuit Board 44a Board surface 46 Resin case 46a Case body 46a1 bottom 46b Lid 46b1 Lid surface 47 Support member 48 Pillar 50 Antenna board 50a Page 1 50b 2nd side 52 Circuit Chip 54 wire 56 Insulating layer 56a First member 56b Second member 60 railroad tracks 62 Resin case 64 Railroad 100 Main body 140 interior space 140a Inner surface C center D diameter L distance W width g1, g2, g3, g4, g5, g6, g7, g8, g9, g10 graphs t, t1, t2 thickness

Claims

1. a power feeding device having a power transmitting antenna disposed in a vehicle; a cushion body made of a dielectric material that constitutes a part of a seat disposed in the vehicle; a sensor provided in the seat; a power receiving antenna circuit that is disposed inside the cushion body, receives the power transmitted from the power transmitting antenna, and outputs the power to be applied to the sensor. Sensor system.

2. The cushion body is a main body; an internal space provided inside the main body and accommodating the power receiving antenna circuit; The sensor system of claim 1 .

3. the main body has a first surface on the power transmitting antenna side and a second surface opposite to the first surface, The internal space is provided near the second surface. The sensor system of claim 2 .

4. An insulating layer having a dielectric loss tangent lower than that of the dielectric material is further provided between the inner surface of the internal space and the outer surface of the power receiving antenna circuit. The sensor system of claim 2 .

5. When the wavelength of the radio wave radiated from the power transmitting antenna is λ, the thickness of the insulating layer is 0.01λ or more and 0.04λ or less. The sensor system of claim 4 .

6. The insulating layer includes a polystyrene foam layer. The sensor system according to claim 4 or claim 5.

7. The insulating layer includes an air layer. The sensor system according to claim 4 or claim 5.

8. a resin case that is housed in the internal space and that defines the insulating layer by housing the power receiving antenna circuit therein; The sensor system of claim 4 .

9. The power receiving antenna circuit includes: an antenna element; an antenna substrate on which the antenna element is mounted, The antenna substrate is a flexible substrate. The sensor system of claim 1 .

10. A portion of the seat includes a headrest. The sensor system according to any one of claims 1 to 5, 8 and 9.

11. A seat disposed in a vehicle, A sensor, a cushion body made of a dielectric material; a power receiving antenna circuit that is disposed inside the cushion body, receives transmitted power from a power transmitting antenna disposed inside the vehicle, and outputs power to be applied to the sensor; seat.

12. A sensor unit provided in a seat arranged in a vehicle, A sensor, a power receiving antenna circuit that receives transmitted power from a power transmitting antenna disposed in the vehicle and outputs power to be provided to the sensor; a resin case that has an internal storage space for storing the power receiving antenna circuit and is disposed inside a cushion body made of a dielectric material that constitutes a part of the seat. Sensor unit.

13. the power receiving antenna circuit has an antenna substrate; a support member provided on the inner surface of the accommodation space to support the antenna board at a position where a predetermined gap is provided between the antenna board and the inner surface; The sensor unit according to claim 12.

14. The support member is a circuit board accommodated in the accommodation space; a support pillar provided on an inner surface of the resin case to support the circuit board against the inner surface; a wire electrically connecting the antenna substrate and the circuit board. The sensor unit according to claim 13.

15. The sensor further includes a line that physically connects the sensor to the resin case that is separate from the sensor and supplies power from the resin case to the sensor. The sensor unit according to claim 12.

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