RFID tag and tire

Abstract

The purpose of the present invention is to improve antenna gain. An RFID tag (1) is provided with a spring antenna (2) and a coupling module (3). The coupling module (3) has a helical antenna and an RFIC element. The spring antenna (2) has a helical coupling part (20), a helical first radiating part (21), a helical second radiating part (22), a first intermediate part (23), and a second intermediate part (24). The coupling module (3) is disposed on the inside of the coupling part (20). The number of turns per length of the coupling module (3) in a direction (D1) parallel to the winding axis (A20) of the coupling part (20) is less than 1 for the first intermediate part (23), and the first intermediate part (23) is positioned between the coupling part (20) and the first radiating part (21). The second intermediate section (24) is positioned between the coupling section (20) and the second radiating section (22), and the number of turns per length of the coupling module (3) in a direction (D1) parallel to the winding axis (A20) of the coupling section (20) is less than 1.

Description

TECHNICAL FIELD

[0001] The present application relates generally to an RFID (Radio frequency Identification) tag and a tire, and more particularly to an RFID tag provided with a coupling module and a tire provided with the RFID tag. BACKGROUND

[0002] Patent Literature 1 discloses an RFID tag provided with a spring-like antenna and a power supply module disposed inside the spring-like antenna.

[0003] In the RFID tag disclosed in Patent Literature 1, a power supply module in a cuboid shape elongated in the length direction of the RFID tag is inserted into a spring-like antenna elongated in the length direction of the RFID tag, and an RFID tag is formed.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: International Publication No. 2018 / 101315 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] In an RFID tag, it is required to seek light weight and small size and to ensure a desired communication distance. Therefore, in an RFID tag, it is sometimes desired to improve antenna gain without increasing the inner diameter of the entire spring antenna.

[0009] An object of the present application is to provide an RFID tag and a tire capable of seeking improvement of antenna gain.

[0010] SOLUTION TO PROBLEM

[0011] An RFID tag of one aspect of the present application is provided with a spring antenna and a coupling module. The coupling module has a spiral antenna and an RFIC element. The RFIC element is connected to the spiral antenna. The spring antenna has a spiral-shaped coupling portion, a spiral-shaped first radiating portion, a spiral-shaped second radiating portion, a first intermediate portion, and a second intermediate portion. The coupling portion is provided with the coupling module on the inside. For the first intermediate portion, the number of turns of the length of the coupling module in a direction parallel to the winding axis of the coupling portion is less than 1, and is located between the coupling portion and the first radiating portion. For the second intermediate portion, the number of turns of the length of the coupling module in the direction parallel to the winding axis of the coupling portion is less than 1, and is located between the coupling portion and the second radiating portion.

[0012] One aspect of the present invention provides a tire comprising: an RFID tag as described above; and a tire carcass having the RFID tag embedded therein.

[0013] The effects of the invention

[0014] The RFID tag and tire of the above-described solution of the present invention can improve antenna gain. Attached Figure Description

[0015] Figure 1 This is a perspective view of the RFID tag according to Implementation Method 1.

[0016] Figure 2 This is an enlarged view of the main parts of the RFID tag in Implementation Method 1.

[0017] Figure 3 This is the front view of the RFID tag in Implementation Method 1.

[0018] Figure 4 This is a side view of the RFID tag coupling part and coupling module of Embodiment 1, viewed from a direction parallel to the winding axis of the coupling part.

[0019] Figure 5 This is a three-dimensional view of the coupling module of the RFID tag in Implementation Method 1, obtained by looking through the interior of the coupling module.

[0020] Figure 6 This is a top view of the coupling module of the RFID tag in Implementation Method 1, obtained by looking through the interior of the coupling module.

[0021] Figure 7 The antenna gain-frequency characteristic diagrams are of the RFID tag of Implementation Example 1 and the RFID tags of Comparative Example 1 and Comparative Example 2.

[0022] Figure 8 A is a perspective view of a tire equipped with an RFID tag according to embodiment 1. Figure 8 B is a front view of the main part of a tire equipped with the RFID tag of embodiment 1.

[0023] Figure 9 This is an explanatory diagram showing the positional relationship between the first end and the second end of the coupling part when viewed from a direction parallel to the winding axis of the coupling part, for the spring antenna of the RFID tag in Embodiment 1.

[0024] Figure 10 This is a perspective view of the RFID tag in Implementation Method 2.

[0025] Figure 11 This is a perspective view of the RFID tag according to implementation method 3.

[0026] Figure 12 This is the front view of the RFID tag in Implementation Method 3. Detailed Implementation

[0027] Hereinafter, embodiments 1 to 3 will be described with reference to the accompanying drawings. The drawings referred to in embodiments 1 to 3 below are schematic drawings, and the size and thickness of the constituent elements in the drawings are not necessarily limited to reflecting the actual size, nor are the size ratios and thickness ratios between the constituent elements limited to reflecting the actual size ratios.

[0028] <Implementation Method 1>

[0029] (1) Construction of RFID tags

[0030] like Figure 1 and Figure 2 As shown, the RFID tag 1 of Embodiment 1 includes a spring antenna 2 and a coupling module 3. The coupling module 3 is, for example, a module magnetically coupled to the spring antenna 2. In the RFID tag 1, the coupling module 3 is magnetically coupled to the spring antenna 2.

[0031] For example, such as Figure 8 A and Figure 8 As shown in Figure B, the RFID tag 1 is embedded in the tire carcass 101 of the tire 100. The RFID tag 1 communicates with, for example, an external reading device.

[0032] (1.1) Construction of the coupling module

[0033] like Figure 5 and Figure 6 As shown, the coupling module 3 is, for example, an elongated cuboid in the first direction D31. The length of the coupling module 3 in the first direction D31 is longer than the length in the second direction D32, which is orthogonal to the first direction D31.

[0034] The coupling module 3 has a helical antenna 6 and an RFIC element 7 connected to the helical antenna 6. The helical antenna 6 is an antenna magnetically coupled to the spring antenna 2. The helical antenna 6 is a magnetic field coupling element with the spring antenna 2 and is also an element used in the integrated circuit of the RFIC element 7 of the coupling module 3.

[0035] The coupling module 3 has a printed circuit board 30, a resin block 31, and a protective layer 32. The helical antenna 6 of the coupling module 3 includes: two conductor portions 61a contained in the printed circuit board 30, and multiple (in...) Figure 5 In the example, there are 12) the first connecting conductor part 61b and one intermediate conductor part 61c, and multiple (in Figure 5 In the example, there are 28 metal pins (62), and multiple (in) Figure 5The second connection conductor portions 63 are each formed by a plurality of (for example, 14 in the example) second connection conductor portions 63. The plurality of metal pins 62 are arranged on the printed circuit board 30. More specifically, two of the 28 metal pins 62 are arranged on the two conductor portions 61a, 24 metal pins 62 are respectively arranged on the first end or the second end of any one of the plurality of first connection conductor portions 61b, one metal pin 62 is arranged on the first end of the intermediate conductor portion 61c, and one metal pin 62 is arranged on the second end of the intermediate conductor portion 61c. The RFIC element 7 is arranged on the printed circuit board 30, for example. The resin block 31 is arranged on the printed circuit board 30 so as to cover the side surface of each of the plurality of metal pins 62 and the RFIC element 7. When viewed from the thickness direction D30 of the printed circuit board 30, the plurality of second connection conductor portions 63 are each arranged so as to span two metal pins 62 arranged along a second direction D32 orthogonal to the first direction D31. The protective layer 32 is arranged on the resin block 31 so as to cover the plurality of second connection conductor portions 63.

[0036] The material of each of the two conductor portions 61a, the plurality of first connection conductor portions 61b, and the intermediate conductor portion 61c includes copper, for example. The material of each of the plurality of metal pins 62 includes copper or a copper alloy, for example. In addition, the material of each of the plurality of second connection conductor portions 63 includes copper, for example.

[0037] The material of the resin block 31 includes a resin (for example, an epoxy resin). In addition, the material of the protective layer 32 includes a resin (for example, an epoxy resin, polyimide, or the like), for example.

[0038] In addition, the outer shape of the coupling module 3 is constituted by the printed circuit board 30, the resin block 31, and the protective layer 32, and becomes a quadrangle when viewed from the first direction D31 parallel to the winding axis A6 of the spiral antenna 6 (refer to FIG. 6). Figure 4 and Figure 5 In the RFID tag 1, the length of the diagonal in the outer shape of the coupling module 3 viewed from the first direction D31 can also be shortened, and further the gap between the spiral antenna 6 and the spring antenna 2 can be narrowed, so that the magnetic field coupling between the spiral antenna 6 and the spring antenna 2 is enhanced. Specifically, in order to shorten the length of the diagonal, the outer shape of the coupling module 3 viewed from the first direction D31 can be made, for example, a hexagon by cutting only the corners of the resin block 31, or further an octagon by further cutting the printed circuit board 30, and further the gap between the spiral antenna 6 and the spring antenna 2 can be narrowed. In addition, in the case where the length of the diagonal in the outer shape of the coupling module 3 viewed from the first direction D31 is shortened, chamfering can be performed by barrel polishing the entire coupling module 3, for example.

[0039] As described above, the helical antenna 6 of the coupling module 3 includes two conductor portions 61a, multiple first connecting conductor portions 61b, one intermediate conductor portion 61c, multiple metal pins 62, and multiple second connecting conductor portions 63. The winding axis A6 of the helical antenna 6 is parallel to the first direction D31.

[0040] RFIC element 7 is connected between the first end 611 and the second end 612 of the helical antenna 6. RFIC element 7 is, for example, an RFIC chip. In this embodiment, RFIC element 7 has a first input / output terminal (not shown) and a second input / output terminal (not shown). The first input / output terminal of RFIC element 7 is connected to the first pad electrode 33 of the printed circuit board 30. The second input / output terminal of RFIC element 7 is connected to the second pad electrode 34 of the printed circuit board 30. Thus, RFIC element 7 is connected to the first end 611 of the helical antenna 6 via the first wiring portion 35 of the printed circuit board 30, and to the second end 612 of the helical antenna 6 via the second wiring portion 36 of the printed circuit board 30. Therefore, the coupling module 3 connects an inductor formed by the helical antenna 6 between the first input / output terminal and the second input / output terminal of RFIC element 7.

[0041] (1.2) Spring antenna

[0042] The following is for reference Figures 1 to 4 The spring antenna 2 will be explained.

[0043] The spring antenna 2 functions as a radio wave radiator from the RFID tag 1, and also acts as an antenna booster. The spring antenna 2 is elastically deformable. The spring antenna 2 comprises steel wire (e.g., piano wire or stainless steel wire). The material of the spring antenna 2 includes, for example, steel (e.g., stainless steel).

[0044] The free length of the spring antenna 2 is determined based on half the wavelength of the radio waves used for communication by the RFID tag 1. The communication frequency band of the RFID tag 1 is, for example, the UHF band, specifically 860MHz to 920MHz. The length of the spring antenna 2 is, for example, 60mm.

[0045] like Figure 1 and Figure 3 As shown, the spring antenna 2 has a helical coupling part 20, a helical first radiating part 21, a helical second radiating part 22, a first intermediate part 23, and a second intermediate part 24.

[0046] In a state where the spring antenna 2 is not elastically deformed, the winding axis A20 of the coupling portion 20, the winding axis A21 of the first radiating portion 21, and the winding axis A22 of the second radiating portion 22 are on a straight line. The length H20 of the coupling portion 20, the length H21 of the first radiating portion 21, and the length H22 of the second radiating portion 22 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 are each a free length.

[0047] The coupling portion 20 is provided with the coupling module 3 on the inner side. That is, in the spring antenna 2, the coupling module 3 is provided on the inner side of the coupling portion 20. In the spring antenna 2, the coupling module 3 is provided on the winding axis A20 of the coupling portion 20. The winding axis A20 of the coupling portion 20 is parallel to the winding axis A6 (refer to FIG. 6) of the spiral antenna 6. The winding axis A20 of the coupling portion 20 is parallel to the winding axis A6 of the spiral antenna 6 not only in a case where the winding axis A20 of the coupling portion 20 is strictly parallel to the winding axis A6 of the spiral antenna 6 but also in a case where the winding axis A20 of the coupling portion 20 forms an acute angle of 10 degrees or less with the winding axis A6 of the spiral antenna 6. Figure 5 and Figure 6 The winding axis A20 of the coupling portion 20 is parallel to the winding axis A6 of the spiral antenna 6 not only in a case where the winding axis A20 of the coupling portion 20 is strictly parallel to the winding axis A6 of the spiral antenna 6 but also in a case where the winding axis A20 of the coupling portion 20 forms an acute angle of 10 degrees or less with the winding axis A6 of the spiral antenna 6.

[0048] As shown in FIG. 2, the coupling portion 20 has a first end 201 and a second end 202. In the present embodiment, as shown in FIG. 2, the second end 202 of the coupling portion 20 overlaps the coupling module 3 when viewed from the direction D1 parallel to the winding axis A20 of the coupling portion 20. Figure 2 Figure 4 As shown in FIG. 2, the coupling portion 20 has a first end 201 and a second end 202. In the present embodiment, as shown in FIG. 2, the second end 202 of the coupling portion 20 overlaps the coupling module 3 when viewed from the direction D1 parallel to the winding axis A20 of the coupling portion 20. Figure 4 By overlapping at least one of the first end 201 and the second end 202 of the coupling portion 20 with the coupling module 3 as described above, it is easy to fix the coupling module 3 inside the coupling portion 20 when the coupling module 3 is inserted into the coupling portion 20. For example, it is possible to insert the coupling module 3 into the coupling portion 20 from the first end 201 of the coupling portion 20, fix the coupling module 3 to the coupling portion 20 with an adhesive portion (not shown) made of a resin material having flexibility, such as a silicone-based resin material, and thereby configure the RFID tag 1 of the present embodiment. In the present embodiment, the second end 202 of the coupling portion 20 overlaps the coupling module 3 when viewed from the direction D1 parallel to the winding axis A20 of the coupling portion 20, but it is also possible that the first end 201 overlaps the coupling module 3 when viewed from the direction D1 parallel to the winding axis A20 of the coupling portion 20.

[0049] As shown in FIG. 2, the winding direction D20 of the coupling portion 20 is a right-handed direction when viewed from the direction D1 parallel to the winding axis A20, which is the same as the winding direction (right-handed direction) of the spiral antenna 6. Figure 1 As shown in FIG. 2, the winding direction D20 of the coupling portion 20 is a right-handed direction when viewed from the direction D1 parallel to the winding axis A20, which is the same as the winding direction (right-handed direction) of the spiral antenna 6.

[0050] Figure 3 ​​As shown, the length H20 of the coupling portion 20 is longer than the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20, but can also be equal to or shorter than the length H3 of the coupling module 3.

[0051] In addition, in the present embodiment, the length H20 of the coupling portion 20 is shorter than the length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22, respectively, in the direction D1 parallel to the winding axis A20 of the coupling portion 20, but can also be equal to the length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22, respectively. The electrical length of the helical first radiating portion 21 and the electrical length of the helical second radiating portion 22 are determined based on a half wavelength of an electric wave for communication of the RFID tag 1, respectively.

[0052] In Embodiment 1, the length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22 are equal in the direction D1 parallel to the winding axis A20 of the coupling portion 20. The "length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22 are equal" can also mean that the length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22 are not strictly equal. The "length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22 are equal" includes a case where the length H21 of the first radiating portion 21 is a value of 90% or more and 110% or less of the length H22 of the second radiating portion 22.

[0053] In the present embodiment, as shown in FIG. 1, the length H20 of the coupling portion 20 is longer than the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20. Figure 1 As shown, the winding direction D21 of the first radiating portion 21 is a direction opposite to the winding direction D20 of the coupling portion 20 when viewed in the direction D1 parallel to the winding axis A20 of the coupling portion 20. In addition, the winding direction D22 of the second radiating portion 22 is a direction opposite to the winding direction D20 of the coupling portion 20 when viewed in the direction D1 parallel to the winding axis A20 of the coupling portion 20.

[0054] As shown in FIG. 1, the length H20 of the coupling portion 20 is longer than the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20. Figure 3As shown, the length H23 of the first intermediate portion 23 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 is longer than the length H3 of the coupling module 3, but can be the same as the length H3 of the coupling module 3. For the first intermediate portion 23, the number of turns of the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 is less than 1, and the first intermediate portion 23 is located between the coupling portion 20 and the first radiating portion 21. The "for the first intermediate portion 23, the number of turns of the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 is less than 1" means that the number of turns of the first intermediate portion 23 is less than 1 in the range of the same length as the length H3 of the coupling module 3 in the first intermediate portion 23. Even if the first intermediate portion 23 has a shape twisted in the range of the same length as the length H3 of the coupling module 3, the number of turns is less than 1. In the embodiment 1, the first intermediate portion 23 has a linear shape, and the number of turns of the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 is zero. The first intermediate portion 23 is located on the winding axis A20 of the coupling portion 20. In the embodiment 1, the first intermediate portion 23 constitutes a first connecting portion connecting the coupling portion 20 and the first radiating portion 21.

[0055] As shown, the length H24 of the second intermediate portion 24 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 is longer than the length H3 of the coupling module 3, but can be the same as the length H3 of the coupling module 3. For the second intermediate portion 24, the number of turns of the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 is less than 1, and the second intermediate portion 24 is located between the coupling portion 20 and the second radiating portion 22. The "for the second intermediate portion 24, the number of turns of the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 is less than 1" means that the number of turns of the second intermediate portion 24 is less than 1 in the range of the same length as the length H3 of the coupling module 3 in the second intermediate portion 24. Even if the second intermediate portion 24 has a shape twisted in the range of the same length as the length H3 of the coupling module 3, the number of turns is less than 1. In the embodiment 1, the second intermediate portion 24 has a linear shape, and the number of turns of the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 is zero. The second intermediate portion 24 is located on the winding axis A20 of the coupling portion 20. In the embodiment 1, the second intermediate portion 24 constitutes a second connecting portion connecting the coupling portion 20 and the second radiating portion 22.

[0056] In Embodiment 1, the length H23 of the first intermediate portion 23 and the length H24 of the second intermediate portion 24 are the same in the direction D1 parallel to the winding axis A20 of the coupling portion 20. The "length H23 of the first intermediate portion 23 and the length H24 of the second intermediate portion 24 are the same" can also mean that the length H23 of the first intermediate portion 23 and the length H24 of the second intermediate portion 24 are not strictly the same length. The "length H23 of the first intermediate portion 23 and the length H24 of the second intermediate portion 24 are the same" includes a case where the length H23 of the first intermediate portion 23 is a value of 80% or more and 120% or less of the length H24 of the second intermediate portion 24.

[0057] (2) Method for manufacturing RFID tag

[0058] In the method for manufacturing the RFID tag 1, the first step of preparing the spring antenna 2 and the second step of disposing the coupling module 3 inside the coupling portion 20 of the spring antenna 2 are sequentially performed.

[0059] In the first step, for example, the spring antenna 2 that has been subjected to heat treatment at a predetermined temperature (for example, 400°C) after being shaped from a steel wire (for example, piano wire or stainless steel wire) is prepared. In the spring antenna 2 that has been subjected to heat treatment at the predetermined temperature after being shaped, the dimensional accuracy of each of the coupling portion 20, the first radiating portion 21, the second radiating portion 22, the first intermediate portion 23, and the second intermediate portion 24 is improved because stress at the time of spring deformation processing of the steel wire is released, and an oxidation film containing Fe3O4 is formed on the surface of the steel wire.

[0060] In the second step, the coupling module 3 is inserted from the first intermediate portion 23 side (or the second intermediate portion 24 side) in the direction (direction D1) along the winding axis A20 of the coupling portion 20 inside the coupling portion 20 of the spring antenna 2 having the coupling portion 20, the first radiating portion 21, the second radiating portion 22, the first intermediate portion 23, and the second intermediate portion 24, and the coupling module 3 is fixed to the spring antenna 2. At the time of coupling the coupling module 3 to the spring antenna 2, for example, the coupling portion 20 and the coupling module 3 can be molded using resin or rubber, or the spring antenna 2 and the coupling module 3 can be fixed using an adhesive. Alternatively, a portion of the spring antenna 2 can be bent so that the coupling module 3 does not fall off from the coupling portion 20.

[0061] In the method for manufacturing the RFID tag 1 of the present embodiment, since the first step and the second step can be performed separately, the dimensional accuracy of the spring antenna 2 is improved, and it is possible to prevent a case where a load is applied to the coupling module 3 at the time of insertion of the coupling module 3, compared to a manufacturing method in which the coupling module is disposed around the spring at the middle of spring processing of the steel wire. Thus, the coupling module 3 is less likely to be damaged, and it is possible to improve the manufacturing quality.

[0062] (3) Actions of RFID tags

[0063] In RFID tag 1, when spring antenna 2 receives radio waves (signals) from the UHF communication band, the radio waves are transmitted to helical antenna 6, which is magnetically coupled to spring antenna 2. Therefore, a current corresponding to the signal flows to RFIC element 7. RFIC element 7 operates by receiving the current supplied from helical antenna 6, outputting a current (signal) corresponding to the information stored in the internal storage unit (not shown) of RFIC element 7 to helical antenna 6. The radio wave (signal) corresponding to this current is then radiated outward from spring antenna 2, which is magnetically coupled to helical antenna 6.

[0064] The spring antenna 2 of the RFID tag 1 in Embodiment 1 functions in the same way as an antenna with a dipole structure because there is a first intermediate portion 23 between the coupling portion 20 and the first radiating portion 21, and a second intermediate portion 24 between the coupling portion 20 and the second radiating portion 22.

[0065] (4) Antenna gain-frequency characteristics of RFID tags

[0066] Figure 7 The antenna gain-frequency characteristics of RFID tag 1 of one embodiment of implementation 1, RFID tag of comparative example 1, and RFID tag of comparative example 2 are shown. Figure 7 In this context, "G1" indicates the antenna gain-frequency characteristics of RFID tag 1 in one embodiment. Figure 7 In this context, "R1" represents the antenna gain-frequency characteristic of the RFID tag in Comparative Example 1. Figure 7 In this context, "R2" represents the antenna gain-frequency characteristic of the RFID tag in Comparative Example 2.

[0067] The total length (free length) of the spring antenna of Comparative Example 1 is 60 mm, and the spacing between the springs constituting the spring antenna is larger than the spacing of the spiral coupling portions 20 in one embodiment. The total length (free length) of the spring antenna of Comparative Example 2 is 37 mm, and the spacing between the springs constituting the spring antenna is larger than the spacing of the spiral coupling portions 20 in one embodiment. In the RFID tag of Comparative Example 1, the spacing between the springs constituting the spring antenna is the same as the inner diameter of the springs constituting the spring antenna. Similarly, in the RFID tag of Comparative Example 2, the spacing between the springs constituting the spring antenna is the same as the spacing between the springs constituting the spring antenna in the RFID tag of Comparative Example 1. The inner diameter of the spring-shaped coupling portion 20 of the spring antenna 2 is the same as the inner diameter of the spring constituting the spring antenna of Comparative Example 1 and the inner diameter of the spring constituting the spring antenna of Comparative Example 2.

[0068] according to Figure 7It can be seen that the antenna gain of the RFID tag in Comparative Example 1 is improved compared to that of the RFID tag in Comparative Example 2. Figure 7 In the diagram, “R1”, representing the antenna gain-frequency characteristic of Comparative Example 1, shows the resonant peak of the coupling module around 0.90 GHz, while the peak of the spring antenna appears at a frequency higher than 1.10 GHz (around 1.3 GHz) (not shown). “R2”, representing the antenna gain-frequency characteristic of Comparative Example 2, shows the resonant peak of the coupling module around 0.90 GHz, while the resonant peak of the spring antenna appears around 1.2 GHz (not shown).

[0069] according to Figure 7 It can be seen that, compared with Comparative Example 1, the antenna gain of the RFID tag 1 in one embodiment is further improved. Furthermore, "G1", representing the antenna gain-frequency characteristic of the RFID tag 1 in one embodiment, shows a resonant peak of the coupling module 3 around 0.90 GHz and a resonant peak of the spring antenna 2 around 0.96 GHz. That is, according to... Figure 7 As can be seen, in one embodiment, compared to Comparative Example 1, the coupling coefficient between the coupling module 3 and the spring antenna 2 can be reduced without making the inner diameter of the coupling portion 20 of the spring antenna 2 larger than the inner diameter of the spring antenna in Comparative Example 1. Based on the above, it can be understood that the RFID tag 1 of one embodiment can improve antenna gain in the communication band of the RFID tag 1.

[0070] (5) Tire construction

[0071] like Figure 8 A and Figure 8 As shown in Figure B, the tire 100 of Embodiment 1 includes an RFID tag 1 and a tire carcass 101 with the RFID tag 1 embedded therein. Additionally, the tire 100 also includes a wheel 104. The tire 100 is, for example, a tire used in automobiles or other vehicles.

[0072] The tire carcass 101 contains an electrically insulating elastomer. An elastomer is a polymeric material that exhibits rubber-like elasticity at room temperature. Examples of "elastomers" include thermoplastic elastomers such as diene polymers, polymers containing diene units, silicone, polyurethane, and polyolefins. The tire carcass 101 has a tread 102 and a sidewall 103. An RFID tag 1 is embedded in the sidewall 103 of the tire carcass 101. Specifically, when the RFID tag 1 is embedded in the sidewall 103, metal fibers are arranged radially (radially) in the sidewall 103. Therefore, the RFID tag 1 is configured orthogonally to the metal fibers to reduce the degradation of antenna radiation characteristics caused by the influence of the metal fibers. The RFID tag 1 can be, for example, sealed between two layers of electrically insulating rubber with high affinity to the elastomer in the sidewall 103, or it can be sealed between two layers containing the elastomer.

[0073] (6) Effects

[0074] In the RFID tag 1 of Embodiment 1, the spring antenna 2 has the coupling portion 20, the first radiating portion 21, the second radiating portion 22, the first intermediate portion 23, and the second intermediate portion 24. The first intermediate portion 23 is located between the coupling portion 20 and the first radiating portion 21, and the number of turns of the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 is less than 1. The second intermediate portion 24 is located between the coupling portion 20 and the second radiating portion 22, and the number of turns of the length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20 is less than 1.

[0075] According to the above structure, it is possible to achieve an increase in antenna gain. More specifically, in the RFID tag 1 of Embodiment 1, the current generated in the coupling portion 20 due to the magnetic field coupling of the coupling portion 20 and the spiral antenna 6 of the coupling module 3 is less likely to be radiated as magnetic field energy to the outside in the first intermediate portion 23 and the second intermediate portion 24, and can be efficiently transmitted to the first radiating portion 21 and the second radiating portion 22, and thus it is possible to increase the antenna radiation efficiency and to increase the antenna gain.

[0076] In addition, in the RFID tag 1 of Embodiment 1, the winding direction D21 of the first radiating portion 21 and the winding direction D22 of the second radiating portion 22 are in the opposite direction to the winding direction D20 of the coupling portion 20.

[0077] According to the above structure, in a case where the coupling portion 20, the first radiating portion 21, and the second radiating portion 22 are respectively magnetized, the inductance of the spring antenna 2 changes, the resonance frequency of the spring antenna 2 changes, and the wavelength shortens, it is possible to reduce the influence of magnetization at times. In a case where the influence of magnetization is not a concern, the winding direction D21 of the first radiating portion 21 and the winding direction D22 of the second radiating portion 22 can be made the same as the winding direction D20 of the coupling portion 20.

[0078] The tire 100 of Embodiment 1 is provided with the RFID tag 1 and the tire carcass 101 in which the RFID tag 1 is built in.

[0079] According to the above structure, it is possible to achieve an increase in antenna gain.

[0080] (Embodiment 1 Modification)

[0081] In the modification of Embodiment 1, when viewed from the direction D1 parallel to the winding axis A20 of the coupling portion 20 (see FIG. 1), as shown in FIG. 2, the first radiating portion 21 and the second radiating portion 22 are located on the same side as the coupling portion 20. Figure 1 Figure 9 ​As shown, the angle θ1 formed by the straight line SL1 passing through the winding axis A20 of the coupling portion 20 and the first end 201 of the coupling portion 20 and the straight line SL2 passing through the winding axis A20 of the coupling portion 20 and the second end 202 of the coupling portion 20 is 90 degrees or less.

[0082] According to the above structure, in manufacturing the RFID tag 1, the spring antenna 2 can be stably arranged on a jig or a platform for arranging the spring antenna 2, the coupling module 3 can be easily inserted into the inside of the coupling portion 20 of the spring antenna 2, and the positioning of the coupling module 3 with respect to the coupling portion 20 can be easily performed.

[0083] The modified example of the embodiment 1 can similarly to the RFID tag 1 of the embodiment 1 seek the improvement of the antenna gain.

[0084] (Embodiment 2)

[0085] Reference Figure 10 The RFID tag 1A of the embodiment 2 will be described. With regard to the RFID tag 1A of the embodiment 2, the same components as those of the RFID tag 1 of the embodiment 1 (refer to Figures 1 to 7 , Figure 8 A of the embodiment 1 and B of the embodiment 1) are denoted by the same reference numerals and the description thereof will be omitted. Figure 8

[0086] (1) Structure

[0087] The RFID tag 1A of the embodiment 2 differs from the RFID tag 1 of the embodiment 1 in that the winding axis A21 of the first radiating portion 21 and the winding axis A22 of the second radiating portion 22 are offset with respect to the winding axis A20 of the coupling portion 20 in a direction orthogonal to the direction D1 parallel to the winding axis A20 of the coupling portion 20.

[0088] In the present embodiment, the winding direction (winding direction) D20 of the coupling portion 20 is a right-handed direction (right winding) and the winding direction D21 of the first radiating portion 21 is a left-handed direction (left winding) when viewed from the direction D1 parallel to the winding axis A20 of the coupling portion 20. In the present embodiment, the winding direction D20 of the coupling portion 20 and the winding direction D21 of the first radiating portion 21 are opposite directions, and the winding direction D20 of the coupling portion 20 and the winding direction D22 of the second radiating portion 22 are opposite directions.

[0089] (2) Effects

[0090] ​The RFID tag 1A in Embodiment 2 is the same as the RFID tag 1 in Embodiment 1. The spring antenna 2 has a helical coupling portion 20, a helical first radiating portion 21, a helical second radiating portion 22, a first intermediate portion 23, and a second intermediate portion 24, thus enabling an increase in antenna gain. In addition, in the RFID tag 1A of Embodiment 2, it is easy to arrange the coupling module 3 inside the coupling portion 20.

[0091] In the RFID tag 1A of Embodiment 2, the winding axis A21 of the first radiating part 21 and the winding axis A22 of the second radiating part 22 are offset relative to the winding axis A20 of the coupling part 20 in a direction orthogonal to the direction D1 parallel to the winding axis A20 of the coupling part 20.

[0092] Based on the above structure, when manufacturing the RFID tag 1A, the first radiating part 21 and the second radiating part 22 are less likely to become obstacles when inserting the coupling module 3 into the coupling part 20, so it is easy to insert the coupling module 3 into the coupling part 20.

[0093] Furthermore, in the RFID tag 1A of Embodiment 2, the winding direction D21 of the first radiating part 21 and the winding direction D22 of the second radiating part 22 are opposite to the winding direction D20 of the coupling part 20.

[0094] According to the above structure, when the coupling section 20, the first radiating section 21, and the second radiating section 22 are magnetized respectively, the inductance of the spring antenna 2 changes, and the resonant frequency of the spring antenna 2 changes, causing a shortening of the wavelength, the effect of magnetization can sometimes be reduced. When the effect of magnetization is not a concern, the winding direction D21 of the first radiating section 21 and the winding direction D22 of the second radiating section 22 can be made the same as the winding direction D20 of the coupling section 20.

[0095] (Implementation Method 3)

[0096] Reference Figure 11 and Figure 12 The RFID tag 1B of Embodiment 3 will be described. In the RFID tag 1B of Embodiment 3, compared with the RFID tag 1 of Embodiment 1 (refer to...), Figures 1 to 7 , Figure 8 A and Figure 8 (B) The same constituent elements are labeled with the same reference numerals and the descriptions are omitted.

[0097] (1) Structure

[0098] The RFID tag 1B of Embodiment 3 differs from the RFID tag 1 of Embodiment 1 in that the length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22 are different, and the length H21 of the first radiating portion 21 is longer than the length H22 of the second radiating portion 22.

[0099] (2) Effects

[0100] As with the RFID tag 1 of Embodiment 1, the RFID tag 1B of Embodiment 3 can achieve an increase in antenna gain. In addition, in the RFID tag 1B of Embodiment 3, in the case where the magnetic coupling between the coupling module 3 and the spring antenna 2 is too strong, the coupling value can be adjusted by changing the ratio of the length H21 of the first radiating portion 21 to the length H22 of the second radiating portion 22.

[0101] The above-described Embodiments 1 to 3 and the like are merely one of various embodiments of the present application. As long as the above-described Embodiments 1 to 3 and the like can achieve the object of the present application, various changes can be made in accordance with design and the like, and the embodiments can be appropriately combined.

[0102] (Other Modified Examples)

[0103] For example, the configuration of the coupling module 3 is not limited to Figure 5 and Figure 6 Examples, and can have other configurations.

[0104] The product to which the RFID tag 1 is applied is not limited to the tire 100, and can be, for example, clothes, linen, and the like.

[0105] [Mode]

[0106] The following mode is disclosed in the present specification.

[0107] The RFID tag (1; 1A; 1B) of the first aspect includes a spring antenna (2) and a coupling module (3). The coupling module (3) includes a spiral antenna (6) and an RFIC element (7). The RFIC element (7) is connected to the spiral antenna (6). The spring antenna (2) includes a coupling portion (20), a first radiating portion (21), a second radiating portion (22), a first intermediate portion (23), and a second intermediate portion (24). The coupling module (3) is disposed inside the coupling portion (20). The number of turns of the length (H3) of the coupling module (3) in a direction (D1) parallel to the winding axis (A20) of the coupling portion (20) is less than 1 for the first intermediate portion (23) between the coupling portion (20) and the first radiating portion (21). The number of turns of the length (H3) of the coupling module (3) in the direction (D1) parallel to the winding axis (A20) of the coupling portion (20) is less than 1 for the second intermediate portion (24) between the coupling portion (20) and the second radiating portion (22).

[0108] According to this aspect, the antenna gain can be increased.

[0109] In the RFID tag (1; 1A; 1B) of the second aspect, the length (H23) of the first intermediate portion (23) and the length (H24) of the second intermediate portion (24) are each longer than the length (H3) of the coupling module (3) in a direction (D1) parallel to the winding axis (A20) of the coupling portion (20) in the RFID tag (1; 1A; 1B) of the first aspect.

[0110] According to this aspect, the coupling module (3) can be easily disposed inside the coupling portion (20) of the spring antenna (2) at the time of manufacture, and thus the performance of the spring antenna (2) can be improved.

[0111] In the RFID tag (1A) of the third aspect, the winding axis (A21) of the first radiating portion (21) and the winding axis (A22) of the second radiating portion (22) are offset with respect to the winding axis (A20) of the coupling portion (20) in a direction orthogonal to the direction (D1) parallel to the winding axis (A20) of the coupling portion (20) in the RFID tag (1; 1A; 1B) of the first aspect or the second aspect.

[0112] According to this aspect, the coupling module (3) can be easily inserted inside the coupling portion (20) at the time of manufacture.

[0113] In the RFID tag (1; 1A; 1B) of the fourth aspect, the winding direction (D21) of the first radiating portion (21) and the winding direction (D22) of the second radiating portion (22) are opposite to the winding direction (D20) of the coupling portion (20) in the RFID tag (1; 1A; 1B) of any one of the first aspect to the third aspect.

[0114] According to this mode, in a case where the coupling portion (20), the first radiating portion (21), and the second radiating portion (22) are each magnetized and the magnetic susceptibility rises, the inductance of the spring antenna (2) changes, the resonant frequency of the spring antenna (2) changes, and the wavelength shortens. In this case, the influence of the magnetization can sometimes be offset.

[0115] In the RFID tag (1; 1A; 1B) of the fifth mode, on the basis of any one of the first mode to the fourth mode, the length (H20) of the coupling portion (20) is shorter than the length (H21) of the first radiating portion (21) and the length (H22) of the second radiating portion (22) in the direction (D1) parallel to the winding axis (A20) of the coupling portion (20).

[0116] According to this mode, the coupling coefficient of the coupling portion (20) and the spiral antenna (6) can be reduced, and the magnetic coupling can be weakened.

[0117] In the RFID tag (1; 1A; 1B) of the sixth mode, on the basis of any one of the first mode to the fifth mode, the coupling portion (20) has a first end (201) and a second end (202). The first end (201) or the second end (202) of the coupling portion (20) overlaps the coupling module (3) when viewed in the direction (D1) parallel to the winding axis (A20) of the coupling portion (20).

[0118] According to this mode, when the coupling module (3) is easily disposed inside the coupling portion (20) of the spring antenna (2) at the time of manufacture, the positioning of the coupling module (3) becomes easy, and a case where the coupling module (3) falls off from the coupling portion (20) can be prevented.

[0119] In the RFID tag (1; 1A; 1B) of the seventh mode, on the basis of any one of the first mode to the sixth mode, the spring antenna (2) contains a piano wire or a stainless steel wire.

[0120] According to this mode, the durability of the spring antenna (2) can be improved.

[0121] In the RFID tag (1; 1A; 1B) of the eighth mode, on the basis of the seventh mode, the material of the spring antenna (2) contains Fe3O4.

[0122] According to this mode, an improvement in reliability can be sought.

[0123] The tire (100) of the ninth mode is provided with the RFID tag (1; 1A; 1B) of any one of the first mode to the eighth mode, and a tire carcass (101) in which the RFID tag (1; 1A; 1B) is built in.

[0124] According to this aspect, it is possible to achieve an increase in antenna gain.

[0125] In the tire (100) of the 10th aspect, on the basis of the 9th aspect, the tire carcass (101) contains an electrically insulating elastomer.

[0126] In the tire (100) of the 11th aspect, on the basis of the 10th aspect, the tire carcass (101) has a side wall (103). The RFID tag (1; 1A; 1B) is built into the side wall (103) of the tire carcass (101).

[0127] According to this aspect, during travel of a vehicle equipped with the tire (100), the RFID tag (1; 1A; 1B) is less likely to be subjected to force from the outside, and it is possible to achieve an increase in reliability of the RFID tag (1; 1A; 1B).

[0128] Explanation of Reference Numerals

[0129] 1, 1A, 1B, RFID tag; 2, spring antenna; 20, coupling portion; 201, 1st end; 202, 2nd end; 21, 1st radiating portion; 22, 2nd radiating portion; 23, 1st intermediate portion; 24, 2nd intermediate portion; 3, coupling module; 6, spiral antenna; 7, RFIC element; 100, tire; 101, tire carcass; 103, side wall; A6, winding axis; A20, winding axis; A21, winding axis; A22, winding axis; D1, direction; D20, winding direction; D21, winding direction; D22, winding direction; D31, 1st direction; D32, 2nd direction; H3, length; H20, length; H21, length; H22, length; H23, length; H24, length.

Claims

1. An RFID tag, wherein the RFID tag is provided with: a spring antenna; and a coupling module, the coupling module has: a spiral antenna; and an RFIC element connected to the spiral antenna, the spring antenna has: a spiral-shaped coupling portion in which the coupling module is disposed on the inner side; a spiral-shaped first radiating portion; a spiral-shaped second radiating portion; a first intermediate portion for which the number of turns of the length of the coupling module in a direction parallel to the winding axis of the coupling portion is less than 1, the first intermediate portion being located between the coupling portion and the first radiating portion; and a second intermediate portion for which the number of turns of the length of the coupling module in the direction parallel to the winding axis of the coupling portion is less than 1, the second intermediate portion being located between the coupling portion and the second radiating portion.

2. The RFID tag according to claim 1, wherein the length of the first intermediate portion and the length of the second intermediate portion are each longer than the length of the coupling module in the direction parallel to the winding axis of the coupling portion.

3. The RFID tag according to claim 1 or 2, wherein the winding axis of the first radiating portion and the winding axis of the second radiating portion are offset with respect to the winding axis of the coupling portion in a direction orthogonal to the direction parallel to the winding axis of the coupling portion.

4. The RFID tag according to any one of claims 1 to 3, wherein the winding direction of the first radiating portion and the winding direction of the second radiating portion are directions opposite to the winding direction of the coupling portion.

5. The RFID tag according to any one of claims 1 to 4, wherein the length of the coupling portion is shorter than the length of the first radiating portion and the length of the second radiating portion in the direction parallel to the winding axis of the coupling portion.

6. The RFID tag according to any one of claims 1 to 5, wherein the coupling portion has a first end and a second end, the first end or the second end of the coupling portion overlaps the coupling module when viewed in the direction parallel to the winding axis of the coupling portion.

7. The RFID tag according to any one of claims 1 to 6, wherein the spring antenna contains piano wire or stainless steel wire.

8. The RFID tag according to claim 7, wherein the material of the spring antenna contains Fe3O4.

9. A tire, wherein the tire is provided with: the RFID tag according to any one of claims 1 to 8; and a tire carcass in which the RFID tag is built in.

10. The tire according to claim 9, wherein the tire carcass contains an electrically insulating elastomer.

11. The tire according to claim 10, wherein the tire carcass has a sidewall, the RFID tag is built in the sidewall of the tire carcass. ​

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