Antenna device and detection device

Abstract

To provide an antenna device and a detection device capable of obtaining sufficient radiation characteristics even when the antenna device is disposed close to a metal member.SOLUTION: An antenna device includes: an annular first substrate having a first surface and a second surface and a first opening part penetrating between the first surface and the second surface; an annular second substrate having a third surface facing the second surface, a fourth surface located opposite to the third surface, and a second opening part penetrating between the third surface and the fourth surface; an annular antenna element provided on the fourth surface and surrounding the second opening, a first coupling line provided on the third surface and coupled to the antenna element, a first feeding line provided on the second surface, an annular ground layer provided on the first surface and surrounding the first opening part, and a first connecting portion connecting the first coupling line and the first feeding line.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to an antenna device and a detection device. [Background technology]

[0002] Conventionally, there has been a fastening strength detection device characterized by comprising a main body formed in a cylindrical shape through the center of which the shaft of a fastening means can be inserted and which is fastened together with the fastened object by the fastening means, a detection means for detecting the state of distortion of the main body, a transmission unit for wirelessly transmitting the detection value detected by the detection means, a short bar of an appropriate length extending circumferentially around the outer surface of a peripheral wall portion that forms the cylindrical shape of the main body or around an imaginary plane that surrounds the outside of the peripheral wall, and an antenna that is arranged within the outer surface of the peripheral wall portion or the imaginary plane that surrounds the outside of the peripheral wall portion and is formed in a linear or band-like shape with an appropriate length (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-173543 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the antenna of conventional fastening strength detection devices is installed on the peripheral wall, which is the side of the main body, if the antenna is placed close to the metal member, such as when it is installed on top of the metal member inserted into the shaft portion of the fastening means (fastening mechanism), sufficient radiation characteristics may not be obtained and the detected value may not be able to be transmitted wirelessly.

[0005] Therefore, an object of the present invention is to provide an antenna device and a detection device that can obtain sufficient radiation characteristics even when placed in close proximity to a metal member. [Means for solving the problem]

[0006] An antenna device according to an embodiment of the present disclosure includes: an annular first substrate having a first surface and a second surface and a first opening penetrating between the first surface and the second surface; an annular second substrate having a third surface facing the second surface, a fourth surface located opposite the third surface, and a second opening penetrating between the third surface and the fourth surface; an annular antenna element provided on the fourth surface and surrounding the second opening; a first coupling line provided on the third surface and coupled to the antenna element; a first feed line provided on the second surface; an annular ground layer provided on the first surface and surrounding the first opening; and a first connection portion connecting the first coupling line and the first feed line. [Effects of the Invention]

[0007] It is possible to provide an antenna device and a detection device that can obtain sufficient radiation characteristics even when placed in close proximity to a metal member. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a detection device according to an embodiment. [Figure 2A] 1A and 1B are diagrams illustrating an example of a state in which a detection device according to an embodiment is used; [Figure 2B] 1A and 1B are diagrams illustrating an example of a state in which a detection device according to an embodiment is used; [Figure 3A] 10A and 10B are diagrams illustrating an example of another usage state of the detection device according to the embodiment. [Figure 3B] 10A and 10B are diagrams illustrating an example of another usage state of the detection device according to the embodiment. [Figure 4] FIG. 2 is a diagram illustrating a disassembled state of the detection device according to the embodiment. [Figure 5] FIG. 2 is a diagram illustrating an example of a configuration of a circuit board unit of the detection device according to the embodiment. [Figure 6A] FIG. 2 is a diagram illustrating an example of a configuration of an upper surface side of a lower wiring substrate of the detection device according to the embodiment. [Figure 6B] FIG. 2 is a diagram illustrating an example of a configuration of a lower surface side of a lower wiring substrate of the detection device according to the embodiment. [Figure 7A] FIG. 2 is a diagram illustrating an example of a configuration of an upper surface side of an upper wiring substrate of the detection device according to the embodiment. [Figure 7B] FIG. 2 is a diagram illustrating an example of a configuration of a lower surface side of an upper wiring substrate of the detection device according to the embodiment. [Figure 8A] FIG. 2 is a diagram illustrating an example of an equivalent circuit of the antenna device according to the embodiment. [Figure 8B] FIG. 2 is a diagram illustrating an example of an equivalent circuit of the antenna device according to the embodiment. [Figure 9] FIG. 2 is a diagram showing an example of an immittance chart showing the impedance of an antenna element. [Figure 10] 10A and 10B are diagrams illustrating an example of a method (part 1) for adjusting the operating frequency and impedance of an antenna element. [Figure 11] 10A and 10B are diagrams illustrating an example of a method (part 2) for adjusting the operating frequency and impedance of an antenna element. [Figure 12A] FIG. 2 is a diagram illustrating an example of a configuration of an upper surface side of an upper wiring substrate of the detection device according to the embodiment. [Figure 12B] FIG. 2 is a diagram illustrating an example of a configuration of a lower surface side of an upper wiring substrate of the detection device according to the embodiment. [Figure 13A] FIG. 10 is a diagram illustrating an example of a simulation result of frequency characteristics of return loss of the detection device according to the embodiment. [Figure 13B] FIG. 10 is a diagram illustrating an example of a simulation result of frequency characteristics of return loss of the detection device according to the embodiment. [Figure 13C] FIG. 10 is a diagram illustrating an example of a simulation result of frequency characteristics of return loss of the detection device according to the embodiment. [Figure 13D] FIG. 10 is a diagram illustrating an example of a simulation result of frequency characteristics of return loss of the detection device according to the embodiment. [Figure 14A] FIG. 10 is a diagram illustrating an example of a simulation result of frequency characteristics of return loss of the detection device according to the embodiment. [Figure 14B] FIG. 10 is a diagram illustrating an example of a simulation result of frequency characteristics of return loss of the detection device according to the embodiment. [Figure 14C]FIG. 10 is a diagram illustrating an example of a simulation result of frequency characteristics of return loss of the detection device according to the embodiment. [Figure 14D] FIG. 10 is a diagram illustrating an example of a simulation result of frequency characteristics of return loss of the detection device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments to which the antenna device and the detection device of the present disclosure are applied will be described. In the following, the same elements will be given the same reference numerals, and duplicated descriptions may be omitted.

[0010] In the following description, an XYZ coordinate system is defined. The direction parallel to the X axis (X direction), the direction parallel to the Y axis (Y direction), and the direction parallel to the Z axis (Z direction) are perpendicular to one another. Planar view refers to viewing from an XY plane. For ease of explanation, the +Z direction is referred to as the upper side and the −Z direction is referred to as the lower side, but this does not represent a universal vertical relationship. In the following description, the length, width, thickness, etc. of each part may be exaggerated to make the configuration easier to understand. The detection device of the embodiment is disk-shaped in plan view. Therefore, in the following description, the radial direction refers to the radial direction of the disk shape of the detection device.

[0011] <Embodiment> <Outline of the detection device 100> 1 is a diagram showing an example of the configuration of a detection device 100 according to an embodiment. The detection device 100 is fixed to a structure with a bolt portion of a fastening mechanism inserted into a through-hole 123 of a flexure body 120 housed in a case 110, and the fastening mechanism and a fastened member abut against the lower and upper surfaces of a main body portion of the flexure body 120 that protrudes upward and downward from the case 110. The lower and upper surfaces of the main body portion of the flexure body 120 protrude in the -Z direction and the +Z direction, respectively, beyond the case 110.

[0012] The detection device 100 may be used in two ways, for example, when the fastening mechanism abuts against the lower surface of the main body of the strain element 120 and the fastened member abuts against the upper surface of the main body, or when the fastened member abuts against the lower surface of the main body of the strain element 120 and the fastening mechanism abuts against the upper surface of the main body. The detection device 100 detects the axial fastening force applied to the bolt when the fastening mechanism fastens the detection device 100 to the fastened member. The detection device 100 outputs a strain detection signal indicating the axial fastening force to the outside via wireless communication.

[0013] <Usage state of the detection device 100> 2A and 2B are diagrams showing an example of a state in which the detection device 100 is in use. 2A and 2B show a fixing part 10, a fastening mechanism 20, and a washer 30. The washer 30 is an example of a fastened member.

[0014] The fixed part 10 is a part of a structure such as a building, a road, a tunnel, or a bridge pier, or a member fixedly attached to a structure. Here, as an example, a form will be described in which the fixed part 10 is the inner wall of a tunnel and is a member made of concrete.

[0015] Washer 30 is a flat metal member, and is fixed by screwing together lock bolt 21 and nut 22 of fastening mechanism 20, with hemispherical washer 25 sandwiched between washer 30 and mounting surface 11 of fixed part 10. Lock bolt 21 has a threaded bolt shank, and is embedded in fixed part 10 to reinforce it. Washer 30 has a through-hole through which the bolt shank passes.

[0016] The fixed part 10 is connected to the ground. That is, the fixed part 10 is connected to the ground. The lock bolt 21 is buried in the fixed part 10 and is therefore connected to the ground. The washer 30 is connected to the lock bolt 21 and is therefore connected to the ground.

[0017] 2A, the detection device 100 is provided between the nut 22 and the washer 30. More precisely, the detection device 100 is provided between the nut 22 and the washer 30 with the hemispherical washer 25 sandwiched between the detection device 100 and the washer 30.

[0018] A lock bolt 21 is inserted through the through hole of the washer 30, the through hole of the hemispherical washer 25, and the through hole 123 (see FIG. 1 ) of the strain body 120 of the detection device 100. The nut 22 is screwed onto the bolt shaft of the lock bolt 21 from the tip side of the lock bolt 21. Note that if the fixing part 10 is a wall part of a building or the like, has a surface opposite to the mounting surface 11, and has a through hole connecting the mounting surface 11 and the surface opposite to it, a bolt may be inserted into the through hole from the opposite surface side instead of the lock bolt 21, and fastened with the nut 22. In this case, the head of the bolt will be located on the surface opposite to the mounting surface 11.

[0019] 2A, when the lock bolt 21 and the nut 22 are fastened, the washer 30 and the detection device 100 are fixed to the fixing part 10. At this time, the lower surface of the main body of the strain element 120 of the detection device 100 abuts against the upper surface 31 of the washer 30 via the hemispherical washer 25, and the upper surface of the main body abuts against the lower surface of the nut 22.

[0020] Therefore, a fastening axial force in the axial direction (Z direction) of the bolt shaft of the lock bolt 21 is applied to the main body of the flexure body 120. Only the lower surface of the main body of the flexure body 120 abuts against the upper surface of the hemispherical washer 25 provided between the upper surface 31 of the washer 30 and the detection device 100, and the lower surface of the case 110 does not abut thereon. Furthermore, only the upper surface of the main body 121 of the flexure body 120 abuts against the lower surface of the nut 22, and the upper surface of the case 110 does not abut thereon. With this configuration, the flexure body 120 can reliably withstand the fastening axial force applied from the nut 22.

[0021] As a result, strain is generated in the strain body 120 according to the tightening torque of the nut 22. The strain generated in the strain body 120 is detected by a plurality of strain sensors provided on the strain body 120 of the detection device 100. The strain can be detected based on the strain detected by each of the plurality of strain sensors (changes in the resistance values ​​of the strain detection elements). A strain detection signal representing the strain is emitted to the outside of the case 110 by a communication unit of the detection device 100. The reader device of the detection device 100 can determine the tightening state of the nut 22 based on the voltage value represented by the strain detection signal received from the detection device 100.

[0022] Furthermore, the lock bolt 21 may be attached at an angle to the mounting surface 11 of the fixed part 10 as shown in Fig. 2B. In other words, the lock bolt 21 may be attached at an angle to the mounting surface 11 of the fixed part 10 as shown in Fig. 2B.

[0023] In such a case, the hemispherical lower surface of the hemispherical washer 25 stably abuts against the upper surface 31 of the washer 30 in response to the tilt, so that the detection device 100 can be stably fixed even when the lock bolt 21 is tilted relative to the mounting surface 11.

[0024] 3A and 3B are diagrams showing an example of another usage state of the detection device 100. In Fig. 3A, a fastening mechanism 20A is used instead of the fastening mechanism 20 shown in Fig. 2A, and the hemispherical washer 25 is not used.

[0025] The fastening mechanism 20A includes a lock bolt 21, a nut 22A, a washer 23, and a bell washer 24. In Fig. 3A, the lower surface of the main body of the flexure element 120 of the detection device 100 abuts against the washer 30. The nut 22A is fastened to the lock bolt 21 via the washer 23 and the bell washer 24. The upper surface of the main body of the flexure element 120 abuts against the lower surface of the washer 23.

[0026] Since bell washer 24 can move in an angled direction relative to washer 23, even when lock bolt 21 is attached at an angle relative to mounting surface 11 of fixed part 10 as shown in Figure 3B, the hemispherical concave inner surface of bell washer 24 and the hemispherical convex outer surface of nut 22A abut according to the inclination of lock bolt 21, and the lower surface of bell washer 24 abuts stably against the upper surface of washer 23, making it possible to stably fix detection device 100.

[0027] <Configuration of the detection device 100> Fig. 4 is a diagram showing the detection device 100 in an exploded state. The right side of Fig. 4 shows an enlarged view of the flexure element 120 and the strain sensor 130. Fig. 5 is a diagram showing an example of the configuration of the circuit board unit 140 of the detection device 100. Fig. 6A is a diagram showing an example of the configuration of the upper surface side of the wiring board 150 of the detection device 100. Fig. 6B is a diagram showing an example of the configuration of the lower surface side of the wiring board 150 of the detection device 100. Since Fig. 6B shows the configuration of the lower surface side of the wiring board 150, the Y direction is opposite to that of Fig. 6A.

[0028] Fig. 7A is a diagram showing an example of the configuration of the upper surface side of wiring substrate 160 of detection device 100. Fig. 7B is a diagram showing an example of the configuration of the lower surface side of wiring substrate 160 of detection device 100. In Fig. 7B, the Y direction is reversed from Fig. 7A in order to show the configuration of the lower surface side of wiring substrate 160.

[0029] The detection device 100 includes a case 110, a strain generator 120, a strain sensor 130, a spacer 141, metal pins 145A and 145B, a wiring board 150, a ground layer 151, feed lines 152, 153, and 154, a wiring board 160, an antenna element 161, coupling lines 170A and 170B, and a circuit section 180.

[0030] Of these components of the detection device 100, the spacer 141, the screw 142, the metal pins 145A and 145B, the wiring board 150, the ground layer 151, the feed lines 152, 153 and 154, the wiring board 160, the antenna element 161, and the coupling lines 170A and 170B form the antenna device 100A.

[0031] Furthermore, among these components of the detection device 100, the spacer 141, the screw 142, the metal pins 145A, 145B, the wiring board 150, the ground layer 151, the power supply lines 152, 153, 154, the wiring board 160, the antenna element 161, the coupling lines 170A, 170B, and the circuit section 180 constitute the circuit board section 140.

[0032] In the detection device 100, the lower side (-Z direction side) is an example of the first side, and the upper side (+Z direction side) is an example of the second side. The direction connecting the first side and the second side is the up-down direction.

[0033] Case 110 is an example of a housing. Metal pin 145A is an example of a first connection portion, and metal pin 145B is an example of a second connection portion. Wiring board 150 is an example of a first substrate, and of feed lines 152, 153, and 154, feed lines 152 and 153 are an example of a first feed line, and feed lines 152 and 154 are an example of a second feed line. Wiring board 160 is an example of a second substrate. Coupled line 170A is an example of a first coupled line, and coupled line 170B is an example of a second coupled line. Circuit unit 180 is an example of a communication unit.

[0034] <Case 110> The case 110 has a lower case 110L and an upper case 110U. Because the detection device 100 performs wireless communication, the case 110 is formed of a dielectric material such as resin. The case 110 has a circular ring shape in a plan view. The case 110 houses at least a portion of the main body 121 of the flexure element 120, a protrusion 122 provided on the side of the main body 121, and the circuit board part 140. The reason that the case 110 houses at least a portion of the main body 121 of the flexure element 120 is because the lower and upper ends of the main body 121 protrude from the case 110.

[0035] <Lower case 110L> The lower case 110L has a lower surface 111L and an opening 112L. The lower surface 111L is the lower surface of the detection device 100, and is also the lower surface of the case 110. However, the lower surface 121A of the strain generating element 120 protrudes downward more than the lower surface 111L. The lower case 110L is, for example, the lower half of the case 110 in the up-down direction.

[0036] The lower case 110L has an opening 112L (see FIG. 4) in the center. The opening 112L is a circular opening in a plan view, and has an opening shape that matches the planar shape of the lower end of the main body 121 of the strain element 120.

[0037] The lower case 110L, together with the upper case 110U, forms an accommodation section, which is a space for accommodating the flexure body 120. The lower end of the main body 121 of the flexure body 120 is inserted into the opening 112L. The size and shape of the opening 112L in a plan view are adjusted so that, when the lower end of the main body 121 of the flexure body 120 is inserted, there is almost no gap between the opening 112L and the outer surface 121C of the lower end of the main body 121. In addition, an O-ring 115L is provided between the opening 112L of the lower case 110L and the flexure body 120, ensuring waterproofing and dustproofing.

[0038] Furthermore, the lower case 110L has a wall surrounding the opening 112L. This wall has a shape that matches the outer circumferential shape of the lower one of the two convex portions 122 of the flexure element 120, and by engaging with the linear portion of the outer periphery of the convex portion 122, it prevents the flexure element 120 from rotating relative to the lower case 110L in a plan view.

[0039] The lower case 110L also accommodates the lower half of the circuit board unit 140 radially outward from the portion where the flexure element 120 is disposed. In this state, the flexure element 120 is accommodated in the central opening of the circuit board unit 140.

[0040] <Upper case 110U> The upper case 110U has the same shape as the lower case 110L in a plan view, and has an upper surface 111U and an opening 112U. As an example, the upper case 110U is the upper half of the case 110 in the vertical direction, and has a configuration in which the lower case 110L is turned upside down. The upper surface 111U is the upper surface of the detection device 100, and is also the upper surface of the case 110. However, the upper surface 121B of the strain generating body 120 protrudes upward more than the upper surface 111U.

[0041] Although a configuration in which the upper case 110U is the upper half of the case 110 in the up-down direction will be described here, the case 110 may be divided at any position in the up-down direction as long as it can accommodate the circuit board unit 140 and the portion of the main body 121 of the strain element 120 other than the upper and lower ends when the upper case 110U and the lower case 110L are combined. Also, the case 110 is not limited to a configuration in which it is divided into upper and lower parts, and may be divided, for example, along a diameter passing through the center of a circle in a plan view.

[0042] The opening 112U is formed in the same position as the opening 112L of the lower case 110L in a plan view, and has the same opening shape. The upper end of the main body 121 of the flexure element 120 is inserted into the opening 112U. The size and shape of the opening 112U in a plan view are adjusted so that, when the upper end of the main body 121 of the flexure element 120 is inserted, there is almost no gap between the opening 112U and the outer surface 121C of the upper end of the main body 121. In addition, an O-ring 115U is provided between the opening 112U of the upper case 110U and the flexure element 120, ensuring waterproof and dustproof properties.

[0043] Additionally, upper case 110U has a wall surrounding opening 112U. This wall has a shape that matches the outer circumferential shape of upper convex portion 122 of two convex portions 122 of flexure element 120, and by engaging with the linear portion of the outer periphery of convex portion 122, it prevents flexure element 120 from rotating relative to upper case 110U in plan view.

[0044] The upper case 110U also accommodates the upper half of the circuit board unit 140 radially outward from the portion where the flexure element 120 is disposed. In this state, the flexure element 120 is accommodated in the central opening of the circuit board unit 140.

[0045] With the strain body 120 and circuit board unit 140 mounted inside the lower case 110L, the upper case 110U is fixed to the lower case 110L as shown in FIG. 1 by inserting screws 118 (see FIG. 4) into the screw holes and fastening the screws 118 to the screw holes of the lower case 110L via O-rings 116 (see FIG. 4) for ensuring waterproofing and dustproofing. At this time, an O-ring 117 is sandwiched between the outer periphery of the lower case 110L and the outer periphery of the upper case 110U, thereby sealing and ensuring waterproofing and dustproofing. At this time, recesses on the outer peripheries of the wiring boards 150 and 160 of the circuit board unit 140 engage with the screw holes of the lower case 110L, so that the circuit board unit 140 is fixed in place without shifting while housed in the case 110.

[0046] In the case 110 as described above, the lower surface 121A of the main body 121 of the flexure body 120 is exposed from the opening 112L of the lower case 110L, and the upper surface 121B of the main body 121 of the flexure body 120 is exposed from the opening 112U of the upper case 110U. Therefore, with regard to the flexure body 120, the case 110 exposes the lower end portion (the portion on the lower surface 121A side) and the upper end portion (the portion on the upper surface 121B side) of the main body 121, and houses the rest of the parts.

[0047] <String body 120> The flexure element 120 has a main body 121, two protrusions 122, and a through-hole 123. The flexure element 120 is preferably made of a metal material such as stainless steel.

[0048] Main body 121 is a portion surrounding through-hole 123, and has lower surface 121A located at the lower end, upper surface 121B located at the upper end, and outer surface 121C. Lower surface 121A is an example of a first end surface, and upper surface 121B is an example of a second end surface. Of main body 121, the lower end portion on the lower side where lower surface 121A is located is an example of a first end portion, and the upper end portion on the upper side where upper surface 121B is located is an example of a second end portion. Main body 121 is a cylindrical portion, and has through-hole 123 that is circular in plan view provided in the center.

[0049] A lower end of main body 121 is inserted through opening 112L of lower case 110L, and lower surface 121A protrudes downward beyond lower surface 111L of lower case 110L. An upper end of main body 121 is inserted through opening 112U of upper case 110U, and upper surface 121B protrudes upward beyond upper surface 111U of upper case 110U.

[0050] The outer surface 121C is the outer side surface of the cylindrical main body 121, and is provided with two protrusions 122 in the center in the Z direction. The two protrusions 122 are provided spaced apart in the up-down direction in the center in the Z direction of the outer surface 121C.

[0051] Strain sensors 130 are provided in a portion of the outer surface 121C between the two protrusions 122. As an example, eight strain sensors 130 are provided, including four strain sensors 130 for detecting strain in the Z-axis direction and four strain sensors 130 for detecting strain in the X- or Y-direction. The eight strain sensors 130 are provided at four locations at 90-degree intervals around the circumferential direction of the outer surface 121C, with one strain sensor 130 for detecting strain in the Z-axis direction and one strain sensor 130 for detecting strain in the X- or Y-direction paired together. The portion of the outer surface 121C where the strain sensors 130 are provided may be a flat surface. The four flat surfaces are provided at equal intervals around the circumferential direction of the outer surface 121C. That is, the four flat surfaces are provided at 90-degree intervals around the circumferential direction of the outer surface 121C.

[0052] Convex portion 122 protrudes outward from outer surface 121C in plan view, and is located above lower surface 121A and below upper surface 121B in the vertical direction. Therefore, outer surface 121C is located above and below two convex portions 122, and outer surface 121C is also located between two convex portions 122.

[0053] The protrusions 122 are annular portions that protrude radially outward from the outer surface 121C, and part of the outer periphery is chamfered at, for example, four locations at 90-degree intervals to prevent rotation inside the lower case 110L and the upper case 110U. The lower case 110L and the upper case 110U engage with the chamfered portions, thereby fixing the protrusions 122 so as not to rotate inside the case 110. Furthermore, the two protrusions 122 abut against the inner walls of the lower case 110L and the upper case 110U in the Z direction, thereby preventing the flexure element 120 from shifting in the Z direction inside the case 110. Furthermore, the protrusions 122 are larger than the openings 112L and 112U of the lower case 110L and the upper case 110U, and therefore the flexure element 120 can be prevented from falling off from the openings 112L or 112U.

[0054] The through hole 123 penetrates the center of the main body 121 in a plan view so as to connect the lower surface 121A and the upper surface 121B. The lock bolt 21 of the fastening mechanism 20 is inserted through the through hole 123, and therefore the through hole 123 has an opening size that matches the planar size of the lock bolt 21. The through hole 123 is a cylindrical hole, and connects the lower surface 121A and the upper surface 121B of the strain element 120.

[0055] As an example, as shown in FIG. 2A, when washer 30 abuts against lower surface 121A of elastic body 120 via hemispherical washer 25 and fastening mechanism 20 abuts against upper surface 121B, a fastening axial force is applied in the direction penetrating through through hole 123 (Z direction), and elastic body 120 is compressed in the up-down direction, causing elastic body 120 to bend so that outer surface 121C bulges outward, resulting in distortion.

[0056] <Strain sensor 130> The strain sensor 130 is provided on the outer surface 121C of the main body 121 of the flexure body 120, in a portion between the two protrusions 122. The strain sensor 130 has one or more strain detection elements and detects the strain of the flexure body 120. For example, each strain detection element uses a strain resistance element whose resistance value changes depending on the amount of strain. Four strain detection elements may be provided and connected in a bridge configuration.

[0057] The strain detection elements may be formed on the outer surface 121C by printing a composite resistor containing cermet or a composite resistor whose binder is synthetic resin. In this case, the strain detection elements can be easily and reliably formed at predetermined installation positions on the outer surface 121C. In particular, since the printing, drying, and curing of the strain detection elements can be performed collectively on the multiple flexure bodies 120 while the multiple flexure bodies 120 are arranged side by side, the strain detection elements can be easily and reliably formed on the multiple flexure bodies 120.

[0058] Furthermore, for example, the strain detection element may be mounted on a rigid or flexible substrate and then attached to the outer surface 121C together with the rigid or flexible substrate. In this case, too, the strain detection element can be easily and reliably installed at a predetermined installation position on the outer surface 121C. Note that the portion of the outer surface 121C where the strain detection element is provided is preferably flat.

[0059] <Spacer 141 and screw 142> The spacers 141 are components that connect the wiring boards 150 and 160. The wiring boards 150 and 160 are joined together by a plurality of screws 142. The four spacers 141 are aligned with the four screw holes 150B of the wiring board 150 and the four screw holes 160B of the wiring board 160 (see FIG. 5 ), and are fixed between the wiring boards 150 and 160 by screws 142 inserted into the four screw holes 150B and screws 142 (not shown) inserted into the four screw holes 160B. By fixing the four spacers 141 between the wiring boards 150 and 160 in this manner, the wiring boards 150 and 160 are mechanically joined together. Since the lengths of the four spacers 141 are equal, the wiring boards 150 and 160 are parallel, and the distance between the wiring boards 150 and 160 is constant. The spacers 141 are made of an insulating material, such as resin, for example.

[0060] <Metal pins 145A and 145B> The lower end of metal pin 145A is inserted into a through-hole provided between lands 151A and 156A of wiring board 150, and the upper end is inserted into a through-hole provided between coupled line 170A and land 162A of wiring board 160, and they are fixed by soldering. In this way, metal pin 145A electrically connects feed line 153 and coupled line 170A.

[0061] The lower end of the metal pin 145B is inserted into a through-hole provided between the lands 151B and 156B of the wiring board 150, and the upper end is inserted into a through-hole provided between the coupled line 170B and the land 162B of the wiring board 160, and the metal pin 145B is fixed by soldering. In this way, the metal pin 145B electrically connects the feed line 154 and the coupled line 170B.

[0062] For example, such metal pins 145A and 145B can be made of copper, brass, etc. Also, instead of the metal pins 145A and 145B, a conducting wire made of copper or the like may be used.

[0063] <Wiring board 150> As an example, wiring board 150 is a wiring board conforming to FR-4 (Flame Retardant type 4) standards. Wiring board 150 has an annular shape in a plan view and is housed in lower case 110L. In FIGS. 6A and 6B, the point where two dashed lines intersect at right angles represents the center of the annular shape of wiring board 150. Wiring board 150, along with wiring board 160, is parallel to the XY plane. The lower surface of wiring board 150 is an example of a first surface, and the upper surface is an example of a second surface.

[0064] The wiring substrate 150 has an annular shape with an opening 150A in the center, and has, for example, six notches provided along the circumferential direction on the inner periphery and eight notches provided along the circumferential direction on the outer periphery. The opening 150A is an example of a first opening that penetrates between the lower surface (first surface) and the upper surface (second surface). The diameter of the opening 150A is set to a value that allows the lock bolt 21 to be inserted therethrough, and is the same as the diameter of the opening 160A of the wiring substrate 160.

[0065] The six notches on the inner periphery and the eight notches on the outer periphery are provided to avoid the 14 protrusions that have the 14 screw holes of the lower case 110L. The wiring board 150 is fixed inside the lower case 110L by the 14 notches engaging with the 14 protrusions.

[0066] For example, wiring board 150 does not have an inner layer. A ground layer 151 is provided on the entire lower surface (see FIG. 6B) of wiring board 150. Two lands 151A and 151B are provided on ground layer 151. For example, ground layer 151 is made of copper foil. Lands 151A and 151B are surrounded by ground layer 151 but are separated from ground layer 151. When ground layer 151 is fabricated, portions of a single copper foil are separated from ground layer 151 and used as lands 151A and 151B.

[0067] <Land 151A, 151B> Land 151A is connected to land 156A on the upper surface of wiring board 150 via a through hole that penetrates wiring board 150 in the thickness direction (Z direction), and land 151B is connected to land 156B on the upper surface of wiring board 150 via a through hole that penetrates wiring board 150 in the thickness direction (Z direction).

[0068] <Power supply lines 152 to 154, power supply circuit 155, lands 156A and 156B, and a plurality of terminals 157> On the upper surface of wiring board 150 (see FIG. 6A), there are provided power supply circuit 155 configured with power supply lines 152 to 154, lands 156A and 156B, and a plurality of terminals 157. Power supply lines 152 to 154, lands 156A and 156B, and a plurality of terminals 157 can be fabricated, for example, by patterning copper foil.

[0069] The feed lines 152 to 154 overlap with the ground layer 151 on the lower surface of the wiring board 150, forming a microstrip line. The feed line 152 is connected to the circuit unit 180 and branches into feed lines 153 and 154 at point A. Therefore, a signal output from the circuit unit 180 is distributed to the feed lines 153 and 154. As shown in FIG. 6A , the feed lines 153 and 154 extend along an arc of radius r from the center of the circular shape of the wiring board 150. A land 156A is connected to the tip of the feed line 153, and a land 156B is connected to the tip of the feed line 154.

[0070] The characteristic impedance of the feed line 152 is, for example, 50 Ω. This is set to the impedance of the high-frequency input / output terminal to which the feed line 152 is connected to the circuit unit 180, which is 50 Ω. The characteristic impedance of the feed lines 153 and 154 is, for example, 100 Ω. Because the feed lines 153 and 154 are connected to the feed line 152 at point A, the combined characteristic impedance of the feed lines 153 and 154 is 50 Ω when viewed from point A.

[0071] If the electrical length of the wavelength of radio waves at the operating frequency of antenna element 161 is λe, the length of feed line 154 is λe / 4 longer than the length of feed line 153. Therefore, the phase of the signal transmitted from circuit unit 180 to land 156B is delayed by π / 2 (rad) from the phase of the signal transmitted from circuit unit 180 to land 156A. This is to enable circularly polarized radio waves to be radiated from antenna element 161. Details of this will be described later. The operating frequency of antenna element 161 is, for example, a frequency included in the 920 MHz band.

[0072] The feeder line 152 may be divided into a feeder line connected to the terminal of the circuit unit 180 and a feeder line connected to the feeder line 153 and a feeder line connected to the feeder line 154 .

[0073] Land 156A is connected to land 151A on the underside of wiring board 150 via a through hole that penetrates wiring board 150 in the thickness direction (Z direction), and land 156B is connected to land 151B on the underside of wiring board 150 via a through hole that penetrates wiring board 150 in the thickness direction (Z direction).

[0074] The lower end of metal pin 145A (see FIG. 5) is inserted into the through-hole between lands 156A and 151A and fixed by soldering. The lower end of metal pin 145B (see FIG. 5) is inserted into the through-hole between lands 156B and 151B and fixed by soldering.

[0075] The plurality of terminals 157 (see FIG. 6A) are terminals to which lead wires connected to the strain sensor 130 are connected. The plurality of terminals 157 are connected to the circuit section 180 via wiring (not shown) provided on the upper surface of the wiring board 150.

[0076] <Wiring board 160> As an example, wiring board 160 is a wiring board conforming to FR-4 standards, similar to wiring board 150. Wiring board 160 has an annular shape in plan view, similar to wiring board 150, and is housed in upper case 110U. In FIGS. 7A and 7B, the point where two dashed lines intersect at right angles indicates the center of the annular shape of wiring board 160. The bottom surface of wiring board 160 is an example of a third surface, and the top surface is an example of a fourth surface. The bottom surface of wiring board 160 faces the top surface of wiring board 150.

[0077] The wiring board 160 has an annular shape with an opening 160A in the center, and six openings, for example, are provided along the circumferential direction, and twelve notches are provided along the periphery. The openings 160A are an example of a second opening that penetrates between the lower surface (third surface) and the upper surface (fourth surface). The upper case 110U has fourteen screw holes (see FIG. 4) and fourteen protrusions that protrude downward from the lower surface of the upper case 110U. The fourteen screw holes penetrate each of the fourteen protrusions. The six openings and eight of the twelve notches are provided to avoid the fourteen protrusions of the upper case 110U.

[0078] When lower case 110L and upper case 110U are aligned with circuit board unit 140 sandwiched therebetween, the upper ends of the 14 protrusions of lower case 110L abut against the lower ends of the 14 protrusions of upper case 110U. In this state, when screws 118 are inserted into the screw holes of upper case 110U, the tips of screws 118 that have passed through the protrusions of upper case 110U enter the interiors of the protrusions of lower case 110L, thereby fastening lower case 110L and upper case 110U together. In this state, circuit board unit 140 is fixed in the Z direction between lower case 110L and upper case 110U, and wiring boards 150 and 160 are fixed in place by the 14 protrusions of lower case 110L and upper case 110U to prevent misalignment.

[0079] <Antenna element 161> Antenna element 161 is formed on the upper surface of wiring board 160 (see FIG. 7A). Antenna element 161 has an annular shape with an inner diameter a and an outer diameter b, and the outer periphery at the position of outer diameter b is located radially inward of the outer periphery of wiring board 160. Antenna element 161 can be produced, for example, by patterning copper foil formed on the upper surface of wiring board 160.

[0080] Antenna element 161 is annular, but has twelve notches on its outer periphery so as to avoid the twelve notches on the outer periphery of wiring board 160. The twelve notches of antenna element 161 are formed along the circumferential direction on the outer periphery of antenna element 161.

[0081] As an example, antenna element 161 is an antenna element for a patch antenna. Although ground layer 151 (see FIG. 6B) exists below antenna element 161, washer 30, which is located further below, is larger than ground layer 151 in plan view, and therefore washer 30 serves as the ground layer of the patch antenna. In other words, antenna element 161 is capacitively coupled with washer 30 to form a patch antenna.

[0082] Here, there are various wireless communication methods for the communication unit included in the circuit unit 180 that supplies power to the antenna element 161, such as RFID (Radio Frequency Identifier) ​​and LPWA (Low Power Wide Area), but here we will explain the RFID form as an example.

[0083] In such a case, the antenna element 161 is required to have the following performance, for example: Resonate at approximately 920 MHz and ensure sufficiently low return loss. Meet the 920 MHz RFID frequency band (7 MHz from 916 MHz to 923 MHz). Obtain a gain of approximately 4 dBi. Be able to radiate circularly polarized waves. In this embodiment, there is provided an antenna device 100A and a detection device 100 that include an antenna element 161 that meets these performance requirements.

[0084] <Lands 162A and 162B> In plan view, lands 162A and 162B (see FIG. 7A) are formed inside two of the twelve cutouts of wiring board 160. As an example, lands 162A and 162B can be produced together with antenna element 161 by patterning copper foil formed on the upper surface of wiring board 160.

[0085] Land 162A is connected to coupled line 170A (see FIG. 7B) provided on the lower surface of wiring board 160 via a through hole that penetrates wiring board 160 in the thickness direction (Z direction). Land 162B is connected to coupled line 170B (see FIG. 7B) provided on the lower surface of wiring board 160 via a through hole that penetrates wiring board 160 in the thickness direction (Z direction).

[0086] <Coupled line 170A, 170B> The coupled lines 170A and 170B are formed on the lower surface of the wiring substrate 160. The coupled lines 170A and 170B are arranged at positions spaced 90 degrees apart from the center of the annular shape of the wiring substrate 160 in the circumferential direction of the annular shape of the wiring substrate 160.

[0087] The coupled lines 170A and 170B extend along the radial direction of the annular shape of the wiring board 160. The lengths of the coupled lines 170A and 170B along the radial direction are equal to each other and are equal to or less than ¼ of the electrical length λe of the wavelength of radio waves at the operating frequency of the antenna element 161. When the lengths of the coupled lines 170A and 170B are equal to or less than λe / 4, the coupled lines 170A and 170B become equivalent to a parallel capacitance connected in parallel to the antenna element 161, and can adjust the impedance of the antenna element 161 in a resonant state. This will be described in detail later.

[0088] The radially outer end of coupled line 170A is connected to land 162A via a through hole that penetrates wiring board 160 in the thickness direction (Z direction). The radially outer end of coupled line 170B is connected to land 162B via a through hole that penetrates wiring board 160 in the thickness direction (Z direction). The radially outer ends of coupled lines 170A and 170B function as lands.

[0089] The upper end of metal pin 145A (see FIG. 5) is inserted into the through-hole between land 162A and coupled line 170A and fixed by soldering. The upper end of metal pin 145B (see FIG. 5) is inserted into the through-hole between land 162B and coupled line 170B and fixed by soldering.

[0090] Therefore, the coupled line 170A is connected to the circuit unit 180 via a feed path formed by the metal pin 145A, the land 156A, the feed line 153, and the feed line 152. The coupled line 170B is connected to the circuit unit 180 via a feed path formed by the metal pin 145B, the land 156B, the feed line 154, and the feed line 152.

[0091] The coupled lines 170A and 170B are capacitively coupled to the antenna element 161. Therefore, the antenna element 161 is fed with power at the portion where the coupled lines 170A and 170B overlap. Furthermore, the length of the feed path between the circuit unit 180 and the coupled line 170B is longer by λe / 4 than the length of the feed path between the circuit unit 180 and the coupled line 170A. Therefore, the phase of the signal transmitted from the circuit unit 180 to the coupled line 170B is delayed by π / 2 (rad) from the phase of the signal transmitted from the circuit unit 180 to the coupled line 170A. In other words, the phase difference is π / 2 (rad), and the signal transmitted from the circuit unit 180 to the coupled line 170B is delayed in phase from the signal transmitted from the circuit unit 180 to the coupled line 170A.

[0092] When a transmission signal is transmitted from circuit unit 180 to coupled lines 170A and 170B, coupled line 170B supplies power to antenna element 161 with a delay of π / 2 (rad) compared to coupled line 170A. The amplitudes of the transmission signals output from coupled lines 170A and 170B to antenna element 161 are the same. Therefore, antenna device 100A and detection device 100 radiate left-handed circularly polarized radio waves in the Z direction.

[0093] In the above description, the coupled lines 170A and 170B shown in FIG. 7B are connected to the lands 162A and 162B (see FIG. 7A) via through-holes at their radially outer ends. However, the positions of the lands 162A and 162B may be moved radially inward, and the radially inner ends of the coupled lines 170A and 170B may be connected to the lands 162A and 162B via through-holes. In this case, the positions of the lands 151A and 151B (see FIG. 6B) and the lands 156A and 156B (see FIG. 6A) may also be moved radially inward.

[0094] <Circuit section 180> The circuit section 180 is connected to the power supply circuit 155 and is also connected to the strain sensor 130 via wiring (not shown). The circuit section 180 incorporates a control section that generates a strain detection signal that indicates the degree of strain of the strain element 120 based on the output of the strain sensor 130, and a communication section that performs wireless communication using the antenna element 161. The detection device 100 is a passive type device that operates without a power source such as a battery, and the circuit section 180 does not have a memory.

[0095] The communication unit generates DC power by rectifying a signal received by the antenna element 161 from the reader device of the detection device 100, and supplies the generated power to the control unit to operate the control unit. The control unit generates a strain detection signal indicating the degree of strain of the strain element 120 and transmits it to the communication unit. The communication unit radiates the strain detection signal as backscatter through the antenna element 161. The radiated strain detection signal is received by the reader device of the detection device 100. As mentioned above, there are various wireless communication methods for the communication unit, such as RFID and LPWA, but here we will explain the RFID form as an example.

[0096] In the above description, the detection device 100 is a passive device that does not have a battery, but the present invention is not limited to this. The detection device 100 may be configured to include at least one of a battery and a memory.

[0097] Furthermore, although the above describes a configuration in which the antenna device 100A radiates left-handed circularly polarized radio waves from the antenna element 161, it may also be configured to radiate right-handed circularly polarized radio waves from the antenna element 161 by swapping the lengths of the feeder lines 153 and 154.

[0098] In the above description, the antenna device 100A includes the metal pins 145A and 145B and the coupling lines 170A and 170B, and the antenna element 161 emits circularly polarized radio waves. However, the antenna device 100A may include only one of the metal pin 145A and the coupling line 170A, or the metal pin 145B and the coupling line 170B, and may emit linearly polarized radio waves from the antenna element 161.

[0099] <Equivalent circuit of antenna device 100A> 8A and 8B are diagrams showing an example of an equivalent circuit of the antenna device 100A. Fig. 8A shows the antenna element 161, the metal pin 145A, the land 156A, and the coupling line 170A. The power feed path that feeds power to the antenna element 161 via the metal pin 145B and the coupling line 170B is the same as the power feed path that feeds power to the antenna element 161 via the metal pin 145A and the coupling line 170A, although the length is different, and is therefore omitted from Fig. 8A.

[0100] 8A, the antenna element 161 is a resonant element in which a resistor Ra, a capacitor Ca, and an inductor La are connected in parallel. The impedance of the antenna element 161 in a resonant state alone is Za. Furthermore, the metal pin 145A is represented as an inductor.

[0101] 8A, the equivalent circuit of antenna device 100A is expressed as a circuit in which antenna element 161 and land 156A are connected via metal pin 145A, and coupling line 170A branches off as an open stub at point B. By adjusting the length (radial length) and width (width relative to the radial length) of coupling line 170A as an open stub, the capacitance between antenna element 161 and coupling line 170A changes.

[0102] The antenna device 100A has a configuration in which the antenna element 161 is excited by utilizing the capacitive coupling between the coupled line 170A and the antenna element 161. The coupled line 170A operates as an open stub of a microstrip line with the antenna element 161 as the ground. Therefore, the antenna device 100A is equivalent to a state in which the coupled line 170A as a capacitance C is connected in parallel to the antenna element 161, and can be represented by the equivalent circuit shown in FIG. 8B.

[0103] The condition for the coupled line 170A to appear as a capacitance C connected in parallel to the antenna element 161 is that the length (radial length) of the coupled line 170A is equal to or less than 1 / 4 of the electrical length λe of the wavelength of the radio wave at the resonant frequency of the antenna element 161.

[0104] <Adjustment of the Impedance of the Antenna Element 161 by the Coupling Lines 170A and 170B> FIG. 9 is a diagram showing an example of an immittance chart showing the impedance of the antenna element 161. As shown in FIG.

[0105] The impedance Za of the antenna element 161 in a resonant state alone is equal to the impedance of the resistor Ra and is greater than 100Ω, i.e., Za=Ra.

[0106] If the length of coupled line 170A is λe / 4 or less, it behaves as a capacitance connected in parallel to antenna element 161, and therefore, by capacitively coupling coupled line 170A to antenna element 161, the point Za=Ra on the immittance chart can be converted to point C. Furthermore, metal pin 145A is connected to coupled line 170A, and metal pin 145A behaves as an inductor, so that it can be converted to the 100Ω point (the center point of the immittance chart).

[0107] The length of the metal pin 145A corresponds to the distance in the Z direction between the wiring boards 150 and 160, and is therefore difficult to freely change. Also, the thickness and material of the metal pin 145A are limited to a certain extent. In other words, it is not easy to adjust the inductance of the metal pin 145A.

[0108] Therefore, the impedance from the antenna element 161 to the metal pin 145A can be adjusted to 100 Ω (the center point of the immittance chart) by adjusting the length (radial length) of the coupled line 170A and thereby adjusting the position of point C. Since the characteristic impedance at the position of the land 156A is 100 Ω, adjusting the impedance from the antenna element 161 to the metal pin 145A to 100 Ω makes it possible to match the impedance from the antenna element 161 to the circuit section 180.

[0109] <How to adjust the operating frequency (resonant frequency) and impedance of the antenna element 161 (Part 1)> 10 is a diagram illustrating an example of a method (part 1) for adjusting the operating frequency and impedance of antenna element 161. Spacing S1 is the vertical spacing between antenna element 161 and ground layer 151, and is approximately equal to the vertical spacing between wiring boards 150 and 160. Spacing S2 is the vertical spacing between antenna element 161 and washer 30, and is approximately equal to the vertical spacing between wiring board 160 and washer 30.

[0110] Here, as an example, a case will be described in which the detection device 100 is fastened to the fixed part 10, which is the inner wall of a concrete tunnel, using a lock bolt 21, a nut 22, and a hemispherical washer 25, as shown in FIG. 2A.

[0111] The spacing S1 is determined by the structure of the detecting device 100, such as the coupling capacitance between the antenna element 161 and the ground layer 151. The spacing S2 is determined by the mounting structure of the detecting device 100 to the fixed part 10 (such as the thickness in the Z direction of the hemispherical washer 25 in FIG. 10). The inner diameter a (see FIG. 7A) of the antenna element 161 is determined by the mounting structure of the detecting device 100 to the fixed part 10 (such as the thickness of the lock bolt 21 in FIG. 10). In other words, the inner diameter a, spacing S1, and spacing S2 are restricted by the dimensions of the structure of the detecting device 100 itself and the dimensions of the mounting structure of the detecting device 100 to the fixed part 10.

[0112] Therefore, in order to adjust the resonant frequency of the antenna element 161 to a desired value (approximately 920 MHz), the outer diameter b, which is not subject to the above-mentioned constraints, is adjusted. Therefore, the outer diameter b of the antenna element 161 is an outer diameter that corresponds to the wavelength of the radio wave at the operating frequency of the antenna element 161.

[0113] Furthermore, the impedance of antenna element 161 is determined by the inner diameter a, outer diameter b, spacing S1, and spacing S2, as well as the radial lengths of coupled lines 170A and 170B. Therefore, to adjust the impedance of antenna element 161 to a desired value (approximately 100Ω), it is sufficient to adjust the radial lengths of coupled lines 170A and 170B under the condition that there are constraints on inner diameter a, spacing S1, and spacing S2.

[0114] <How to adjust the operating frequency (resonant frequency) and impedance of the antenna element 161 (Part 2)> Fig. 11 is a diagram illustrating an example of a method (part 2) for adjusting the operating frequency and impedance of antenna element 161. Fig. 12A is a diagram illustrating an example of the configuration of the upper surface side of wiring board 160 of detection device 100. Fig. 12B is a diagram illustrating an example of the configuration of the lower surface side of wiring board 160 of detection device 100.

[0115] Fig. 11 shows, as an example, the spacing S1 and spacing S3 when detecting device 100 is fastened to fixing portion 10, which is the inner wall of a concrete tunnel, using lock bolt 21, nut 22A, washer 23, and bell washer 24, as shown in Fig. 3A. Figs. 12A and 12B show examples of the configurations of the upper and lower sides, respectively, of wiring board 160 in the mounting structure shown in Fig. 3A.

[0116] 10, and is determined by the structure of the detecting device 100, such as the coupling capacitance between the antenna element 161 and the ground layer 151. The distance S3 is the distance in the vertical direction between the antenna element 161 and the washer 30, and is approximately equal to the distance in the vertical direction between the wiring board 160 and the washer 30. The distance S3 is determined by the mounting structure of the detecting device 100 to the fixed part 10 (such as the length in the Z direction of the lower end of the main body 121 of the strain element 120 in FIG. 11). The distance S3 is narrower than the distance S2 (see FIG. 10), which is restricted by the thickness of the hemispherical washer 25.

[0117] As shown in FIG. 11, in the detection device 100 fastened to the fixed part 10 using a lock bolt 21, a nut 22A, a washer 23, and a bell washer 24, the inner diameter a, the spacing S1, and the spacing S3 are restricted by the dimensions of the structure of the detection device 100 itself and the dimensions of the mounting structure of the detection device 100 to the fixed part 10, just as in the detection device 100 fastened to the fixed part 10 using a lock bolt 21, a nut 22, and a hemispherical washer 25 as shown in FIG.

[0118] The inner diameter a (see FIG. 12A) of antenna element 161 is the same as that in FIG. 7A and is determined by the mounting structure of detection device 100 to fixed part 10 (such as the thickness of lock bolt 21 in FIG. 11). Furthermore, because spacing S3 is narrower than spacing S2 (see FIG. 10), the area of ​​antenna element 161 may be smaller than the area of ​​antenna element 161 shown in FIG. 7A. For this reason, in FIG. 12A, the outer diameter c (see FIG. 12A) of antenna element 161 is made shorter than the outer diameter b shown in FIG. 7A in order to adjust the resonant frequency of antenna element 161 to a desired value (approximately 920 MHz).

[0119] Furthermore, to adjust the impedance of the antenna element 161 to a desired value (approximately 100Ω), the radial lengths of the coupled lines 170A and 170B are adjusted under the condition that the inner diameter a, the spacing S1, and the spacing S3 are constrained. As an example, as shown in FIG. 12B , the radial lengths of the coupled lines 170A and 170B are shorter than those of the coupled lines 170A and 170B shown in FIG. 7B . By adjusting the radial lengths of the coupled lines 170A and 170B in this manner, the impedance of the antenna element 161 can be adjusted to a desired value (approximately 100Ω). Note that, because through holes are provided between the radially outer ends of the coupled lines 170A and 170B and the lands 162A and 162B, the radially outer ends of the coupled lines 170A and 170B shown in FIG. 7B are positioned identically to the radially outer ends of the coupled lines 170A and 170B shown in FIG. 12B .

[0120] <Simulation of the Frequency Characteristics of the Return Loss of the Detection Device 100 (Part 1)> 13A to 13D are diagrams showing an example of a simulation result of the frequency characteristics of the return loss of the detecting device 100. In the simulation (part 1), the S11 parameter of the antenna element 161 viewed from point A (see FIG. 6A) of the detecting device 100 fastened to the fixing part 10 using the lock bolt 21, the nut 22, and the hemispherical washer 25, as shown in FIGS. 2A and 10, was calculated as the return loss of the detecting device 100. In the simulation, the operating frequency (resonant frequency) of the antenna element 161 was set to 920 MHz.

[0121] 13A shows the frequency characteristics of the return loss in the detection device 100 when the lock bolt 21 is perpendicular to the mounting surface 11 of the fixed part 10, as shown in FIG. 2A. FIG. 13B shows the frequency characteristics of the return loss in the detection device 100 when the lock bolt 21 is tilted 10 degrees from the normal to the mounting surface 11 of the fixed part 10, as shown in FIG. 2B. FIG. 13C shows the frequency characteristics of the gain of left-handed circularly polarized waves in the +Z direction when the lock bolt 21 is perpendicular to the mounting surface 11 of the fixed part 10. FIG. 13D shows the frequency characteristics of the gain of left-handed circularly polarized waves in the +Z direction when the lock bolt 21 is tilted 10 degrees in the Y direction from the normal to the mounting surface 11 of the fixed part 10.

[0122] As shown in Figure 13A, when the lock bolt 21 is perpendicular to the mounting surface 11 of the fixed part 10, the S11 parameter was -10 dB or less in the range of 898 MHz to 951 MHz. In the wide band of 53 MHz including 920 MHz, the return loss was low and good results were obtained. The 53 MHz band including 920 MHz includes the RFID band (7 MHz: 916 MHz to 923 MHz) and is much wider than the RFID band.

[0123] Furthermore, as shown in FIG. 13B, when the lock bolt 21 is tilted relative to the mounting surface 11 of the fixed part 10, the S11 parameter was -10 dB or less in the range of 904 MHz to 940 MHz. Low return loss was observed in a wide band of 36 MHz, including 920 MHz, providing favorable results. It was confirmed that broadband communication is possible in the 920 MHz band, even when the lock bolt 21 is tilted relative to the mounting surface 11 of the fixed part 10. The 36 MHz band, including 920 MHz, includes the RFID band (7 MHz: 916 MHz to 923 MHz) and is significantly wider than the RFID band. The gains of left-handed circularly polarized waves in the +Z direction were approximately +7.2 dBi (see FIG. 13C) and approximately +6.2 dBi (see FIG. 13D), respectively, confirming that these were sufficient levels for reliable communication with a reader device.

[0124] <Simulation of the Frequency Characteristics of the Return Loss of the Detection Device 100 (Part 2)> 14A to 14D are diagrams showing an example of a simulation result of the frequency characteristics of the return loss of the detection device 100. In the simulation (part 2), the S11 parameter of the antenna element 161 viewed from point A (see FIG. 6A) of the detection device 100 fastened to the fixing part 10 using the lock bolt 21, the nut 22A, the washer 23, and the bell washer 24 was calculated as the return loss of the detection device 100, as shown in FIGS. 3A and 11. In the simulation, the operating frequency (resonance frequency) of the antenna element 161 was set to 920 MHz.

[0125] 14A shows the frequency characteristics of the return loss in the detection device 100 when the lock bolt 21 is perpendicular to the mounting surface 11 of the fixed part 10, as shown in FIG. 3A. FIG. 14B shows the frequency characteristics of the return loss in the detection device 100 when the lock bolt 21 is tilted 10 degrees from the normal to the mounting surface 11 of the fixed part 10, as shown in FIG. 3B. FIG. 14C shows the frequency characteristics of the gain of left-handed circularly polarized waves in the +Z direction when the lock bolt 21 is perpendicular to the mounting surface 11 of the fixed part 10. FIG. 14D shows the frequency characteristics of the gain of left-handed circularly polarized waves in the +Z direction when the lock bolt 21 is tilted 10 degrees in the Y direction from the normal to the mounting surface 11 of the fixed part 10.

[0126] As shown in FIG. 14A, when the lock bolt 21 is perpendicular to the mounting surface 11 of the fixed part 10, the S11 parameter was −10 dB or less in the range of 911 MHz to 928 MHz. In a wide band of 17 MHz including 920 MHz, the return loss was low, and favorable results were obtained. Compared to the results shown in FIG. 13A, the 920 MHz band is narrower, but this is thought to be due to the effect of the larger coupling capacitance with the washer 30, since the spacing S3 between the antenna element 161 and the washer 30 is narrower than the spacing S2. Even so, the 17 MHz band including 920 MHz includes the RFID band (7 MHz: 916 MHz to 923 MHz) and is more than twice the RFID band.

[0127] Furthermore, as shown in FIG. 14B, when the lock bolt 21 is tilted relative to the mounting surface 11 of the fixed part 10, the S11 parameter was −10 dB or less in the range of 906 MHz to 924 MHz. Low return loss and favorable results were obtained in a wide 18 MHz band including 920 MHz. It was confirmed that broadband communication is possible in the 920 MHz band even when the lock bolt 21 is tilted relative to the mounting surface 11 of the fixed part 10. Compared to the results shown in FIG. 13B, the narrower 920 MHz band is likely due to the large coupling capacitance with the washer 30, as in FIG. 13A. Even so, the 18 MHz band including 920 MHz includes the RFID band (7 MHz: 916 MHz to 923 MHz) and is more than twice the RFID band. Furthermore, the gain of left-handed circularly polarized waves in the +Z direction was approximately +4.6 dBi (see Figure 14C) and approximately +4.4 dBi (see Figure 14D), respectively, confirming that these were levels at which communication with the reader device could be reliably performed.

[0128] <Effects> Antenna device 100A of the present disclosure includes: an annular wiring board 150 having a first surface and a second surface and an opening 150A penetrating between the first surface and the second surface; an annular wiring board 160 having a third surface opposite the second surface, a fourth surface located opposite the third surface, and an opening 160A penetrating between the third surface and the fourth surface; an annular antenna element 161 provided on the fourth surface and surrounding the opening 160A; a coupling line 170A provided on the third surface and coupled to antenna element 161; feed lines 152 and 153 provided on the second surface; an annular ground layer 151 provided on the first surface and surrounding the opening 150A; and a metal pin 145A connecting coupling line 170A and feed lines 152 and 153. In this way, since it includes antenna element 161 provided on wiring board 160 located above wiring board 150 having ground layer 151, sufficient radiation characteristics can be obtained even when it is placed close to a metal member.

[0129] Therefore, even if the antenna device 100A is placed in close proximity to a metal member such as the washer 30, it is possible to provide an antenna device 100A that can obtain sufficient radiation characteristics.

[0130] Furthermore, the coupling line 170A may extend along the radial direction of the antenna element 161. By extending the coupling line 170A along the radial direction, the annular antenna element 161 can be efficiently fed with power.

[0131] The antenna element 161 may further include a coupling line 170B provided on the third surface and coupled to the antenna element 161, feed lines 152 and 154 provided on the second surface, and a metal pin 145B connecting the coupling line 170B and the feed lines 152 and 154. By feeding power to the antenna element 161 at two points, the coupling lines 170A and 170B, it is possible to emit circularly polarized radio waves.

[0132] Furthermore, the coupling line 170B may extend along the radial direction of the antenna element 161. By extending the coupling line 170B along the radial direction, the annular antenna element 161 can be efficiently fed with power.

[0133] Alternatively, metal pin 145A and metal pin 145B may have the same length, and coupled line 170A and coupled line 170B may have the same length, and feed lines 152 and 153 and feed lines 152 and 154 may have a length difference such that a phase difference of π / 2 (rad) occurs between a signal supplied from feed lines 152 and 153 to antenna element 161 via metal pin 145A and coupled line 170A and a signal supplied from feed lines 152 and 154 to antenna element 161 via metal pin 145B and coupled line 170B. By feeding signals with a phase difference of π / 2 (rad) to antenna element 161 at two points on coupled lines 170A and 170B, it is possible to efficiently radiate left-handed circularly polarized or right-handed circularly polarized radio waves.

[0134] The difference in length between the feed lines 152 and 153 and the feed lines 152 and 154 may be ¼ of the electrical length λe of the wavelength of radio waves at the operating frequency of the antenna element 161. When the difference in length between the feed paths from the feed lines 152 and 153 to the coupled line 170A and the feed paths from the feed lines 152 and 154 to the coupled line 170B is λe / 4, it is possible to efficiently radiate left-handed or right-handed circularly polarized radio waves.

[0135] Furthermore, metal pin 145A (first connection portion) and metal pin 145B (second connection portion) may be formed of metal pins, with metal pin 145A connecting coupled line 170A to feed lines 152 and 153, and metal pin 145B connecting coupled line 170B to feed lines 152 and 154. By using metal pins 145A and 145B, feed line 152 can be reliably and stably connected to coupled lines 170A and 170B, and circularly polarized radio waves can be stably emitted.

[0136] Furthermore, the outer diameter (b, c) of the antenna element 161 may be an outer diameter corresponding to the wavelength of radio waves at the operating frequency of the antenna element 161. By adjusting the outer diameter of the antenna element 161, the operating frequency of the antenna element 161 can be set, and it is possible to provide the antenna device 100A that can obtain sufficient radiation characteristics even when it is placed close to a metal member such as the washer 30.

[0137] Furthermore, the length of the coupled line 170A may be equal to or less than ¼ of the electrical length λe of the wavelength of radio waves at the operating frequency of the antenna element 161. When the length is equal to or less than λe / 4, the coupled line 170A behaves as a capacitance connected in parallel to the antenna element 161, and therefore the impedance of the antenna element 161 can be adjusted.

[0138] Furthermore, under the condition that there are dimensional constraints due to the structure of the antenna device 100A or due to the mounting structure of the antenna device 100A to a fixed portion, the length of the coupled line 170A may be set depending on the degree of impedance matching between the antenna element 161, the feed lines 152 and 153, the metal pin 145A, and the coupled line 170A. When the antenna device 100A is mounted on a fixed portion 10 such as the inner wall of a tunnel, the impedance can be adjusted by adjusting the length of the coupled line 170A, and therefore sufficient radiation characteristics can be obtained.

[0139] The detection device 100 of the present disclosure includes: the antenna device 100A described above; a main body 121 having a first end and a second end; a through hole 123 penetrating the main body 121 in a direction connecting a first side (lower side) where the first end is located and a second side (upper side) where the second end is located, and through which a lock bolt 21 of a fastening mechanism 20 is inserted; the strain sensor 130 detecting strain of the strain body 120 due to a fastening axial force applied by the fastening mechanism 20 in the extension direction of the through hole 123; a circuit unit 180 connected to power feed lines 152 and 153 and the strain sensor 130 and performing wireless communication; and a case 110 accommodating at least a portion of the main body 121 of the strain body 120. In this way, since it includes antenna element 161 provided on wiring board 160 located above wiring board 150 having ground layer 151, sufficient radiation characteristics can be obtained even when it is placed close to a metal member.

[0140] Therefore, even when the detector 100 is placed in close proximity to a metal member such as the washer 30, it is possible to provide a detector 100 that can obtain sufficient radiation characteristics.

[0141] The above describes exemplary embodiments of the antenna device and detection device of the present disclosure, but the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and variations are possible without departing from the scope of the claims.

[0142] The following additional notes are provided regarding the above-described embodiments. (Appendix 1) a first annular substrate having a first surface and a second surface and a first opening extending between the first surface and the second surface; a second annular substrate having a third surface opposite to the second surface, a fourth surface opposite to the third surface, and a second opening penetrating between the third surface and the fourth surface; an annular antenna element provided on the fourth surface and surrounding the second opening; a first coupling line provided on the third surface and coupled to the antenna element; a first feed line provided on the second surface; a ring-shaped ground layer provided on the first surface and surrounding the first opening; a first connection portion connecting the first coupled line and the first feed line; An antenna device comprising: (Appendix 2) 2. The antenna device according to claim 1, wherein the first coupling line extends along a radial direction of the antenna element. (Appendix 3) a second coupling line provided on the third surface and coupled to the antenna element; a second feed line provided on the second surface; a second connection portion connecting the second coupled line and the second feed line; 3. The antenna device according to claim 1 or 2, further comprising: (Appendix 4) 4. The antenna device according to claim 3, wherein the second coupling line extends along a radial direction of the antenna element. (Appendix 5) the first connecting portion and the second connecting portion have the same length, and the first coupled line and the second coupled line have the same length; 5. The antenna device according to claim 3, wherein the first feed line and the second feed line have a difference in length such that a phase difference between a signal supplied from the first feed line to the antenna element via the first connection portion and the first coupled line and a signal supplied from the second feed line to the antenna element via the second connection portion and the second coupled line is π / 2 (rad). (Appendix 6) 6. The antenna device according to claim 5, wherein the difference in length between the first feed line and the second feed line is 1 / 4 of the electrical length λe of the wavelength of a radio wave at the operating frequency of the antenna element. (Appendix 7) the first connection portion and the second connection portion are formed by metal pins, the metal pin as the first connection portion connects the first coupled line and the first feed line and fixes the first substrate and the second substrate; The antenna device according to any one of claims 3 to 6, wherein the metal pin as the second connection portion connects the second coupling line and the second feed line and fixes the first substrate and the second substrate. (Appendix 8) 8. The antenna device according to claim 1, wherein the outer diameter of the antenna element corresponds to the wavelength of radio waves at the operating frequency of the antenna element. (Appendix 9) 9. The antenna device according to claim 1, wherein the length of the first coupled line is equal to or less than 1 / 4 of the electrical length λe of the wavelength of a radio wave at the operating frequency of the antenna element. (Appendix 10) The antenna device described in Appendix 9, wherein, under the condition that there are dimensional constraints due to the structure of the antenna device or dimensional constraints due to the mounting structure of the antenna device to a fixed portion, the length of the first coupling line is set according to the degree of impedance matching between the antenna element, the first feed line, the first connection portion, and the first coupling line. (Appendix 11) An antenna device according to any one of Supplementary Notes 1 to 10; a strain generating body having a main body having a first end and a second end, and a through hole penetrating the main body in a direction connecting a first side where the first end is located and a second side where the second end is located, wherein a bolt portion of a fastening mechanism is inserted into the through hole, the first end being inserted into the first opening of the first base plate, and the second end being inserted into the second opening of the second base plate; a strain sensor that detects a strain of the strain-generating body due to a fastening axial force applied in the extending direction of the through hole by the fastening mechanism; a communication unit connected to the first feed line and the strain sensor and configured to perform wireless communication; a case that accommodates at least a portion of the main body of the strain generating body; A detection device comprising: [Explanation of symbols]

[0143] 100 Detection device 100A Antenna Unit 110 cases 120 Strain body 130 Strain Sensor 145A Metal pin (example of first connection part) 145B Metal pin (example of second connection part) 150 wiring board (an example of a first board) 151 Ground Layer 152, 153 Power feeder line (example of first power feeder line) 152, 154 Power feeder line (example of second power feeder line) 160 wiring board (an example of a second board) 161 Antenna element 170A coupled line (example of the first coupled line) 170B coupled line (an example of a second coupled line) 180 Circuit section (example of communication section)

Claims

1. a first annular substrate having a first surface and a second surface and a first opening extending between the first surface and the second surface; a second annular substrate having a third surface opposite the second surface, a fourth surface opposite the third surface, and a second opening penetrating between the third surface and the fourth surface; an annular antenna element provided on the fourth surface and surrounding the second opening; a first coupling line provided on the third surface and coupled to the antenna element; a first feed line provided on the second surface; a ring-shaped ground layer provided on the first surface and surrounding the first opening; a first connection portion connecting the first coupled line and the first feed line; An antenna device comprising:

2. The antenna device according to claim 1 , wherein the first coupling line extends along a radial direction of the antenna element.

3. a second coupling line provided on the third surface and coupled to the antenna element; a second feed line provided on the second surface; a second connection portion connecting the second coupled line and the second feed line; The antenna device of claim 1 further comprising:

4. The antenna device according to claim 3 , wherein the second coupling line extends along a radial direction of the antenna element.

5. the first connecting portion and the second connecting portion have the same length, and the first coupled line and the second coupled line have the same length; 4. The antenna device according to claim 3, wherein the first feed line and the second feed line have a difference in length such that a phase difference between a signal supplied from the first feed line to the antenna element via the first connection portion and the first coupled line and a signal supplied from the second feed line to the antenna element via the second connection portion and the second coupled line is π / 2 (rad).

6. 6. The antenna device according to claim 5, wherein the difference in length between the first feed line and the second feed line is 1 / 4 of an electrical length λe of a wavelength of a radio wave at an operating frequency of the antenna element.

7. the first connection portion and the second connection portion are formed by metal pins, the metal pin as the first connection portion connects the first coupled line and the first feed line and fixes the first substrate and the second substrate; The antenna device according to claim 3 , wherein the metal pin serving as the second connection portion connects the second coupling line and the second feed line and fixes the first substrate and the second substrate together.

8. 2. The antenna device according to claim 1, wherein the outer diameter of the antenna element corresponds to the wavelength of radio waves at the operating frequency of the antenna element.

9. 2. The antenna device according to claim 1, wherein the length of the first coupled line is equal to or less than 1 / 4 of the electrical length λe of the wavelength of radio waves at the operating frequency of the antenna element.

10. 10. The antenna device according to claim 9, wherein, under conditions where there are dimensional constraints due to the structure of the antenna device or dimensional constraints due to the mounting structure of the antenna device to a fixed portion, the length of the first coupling line is set according to the degree of impedance matching between the antenna element, the first feed line, the first connection portion, and the first coupling line.

11. The antenna device according to claim 1; a strain generating body having a main body portion having a first end and a second end, and a through hole penetrating the main body portion in a direction connecting a first side where the first end is located and a second side where the second end is located, wherein a bolt portion of a fastening mechanism is inserted into the through hole, the first end being inserted into the first opening of the first base plate, and the second end being inserted into the second opening of the second base plate; a strain sensor that detects a strain of the strain-generating body due to a fastening axial force applied in the extending direction of the through hole by the fastening mechanism; a communication unit connected to the first feed line and the strain sensor and configured to perform wireless communication; a case that accommodates at least a portion of the main body of the strain generating body; A detection device comprising:

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