WO2025027996A1 - Rfid tag and tire - Google Patents

Abstract

The present invention improves antenna gain. An RFID tag (1) comprises a spring antenna (2) and a coupling module (3). The coupling module (3) includes a helical antenna and an RFIC element. The spring antenna (2) includes a helical coupling part (20), a helical first radiation part (21), a helical second radiation part (22), a first intermediate part (23), and a second intermediate part (24). The coupling part (20) is provided inside the coupling module (3). The first intermediate part (23) is positioned between the coupling part (20) and the first radiation part (21) and has fewer than 1 turn per unit length of the coupling module (3) in the direction (D1) parallel to the winding axis (A20) of the coupling part (20). The second intermediate part (24) is positioned between the coupling part (20) and the second radiation part (22) and has fewer than 1 turn per unit length of the coupling module (3) in the direction (D1) parallel to the winding axis (A20) of the coupling part (20).

Description

RFID tag and tire

The present invention relates generally to radio frequency identification (RFID) tags and tires, and more particularly to an RFID tag having a coupling module and a tire having an RFID tag.

Patent document 1 discloses an RFID tag that includes a spring-shaped antenna and a power supply module that is disposed inside the spring-shaped antenna.

In the RFID tag disclosed in Patent Document 1, a rectangular parallelepiped-shaped power supply module that is elongated in the longitudinal direction of the RFID tag is inserted into a spring-shaped antenna that is elongated in the longitudinal direction of the RFID tag to form the RFID tag.

International Publication No. 2018/101315

RFID tags are required to be lightweight and compact while ensuring the desired communication distance. For this reason, it is sometimes desirable to improve the antenna gain of RFID tags without increasing the inner diameter of the entire spring antenna.

The object of the present invention is to provide an RFID tag and a tire that can improve antenna gain.

An RFID tag according to one aspect of the present invention includes a spring antenna and a coupling module. The coupling module includes a helical antenna and an RFIC element. The RFIC element is connected to the helical antenna. The spring antenna includes a helical coupling portion, a first helical radiating portion, a second helical radiating portion, a first intermediate portion, and a second intermediate portion. The coupling portion has the coupling module disposed inside. The first intermediate portion has less than one turn per length of the coupling module in a direction parallel to the winding axis of the coupling portion, and is located between the coupling portion and the first radiating portion. The second intermediate portion has less than one turn per length of the coupling module in the direction parallel to the winding axis of the coupling portion, and is located between the coupling portion and the second radiating portion.

A tire according to one aspect of the present invention includes an RFID tag according to the above aspect and a tire casing in which the RFID tag is embedded.

The RFID tag and tire according to the above aspect of the present invention can improve the antenna gain.

FIG. 1 is a perspective view of an RFID tag according to a first embodiment. FIG. 2 is an enlarged view of a main part of the RFID tag. FIG. 3 is a front view of the RFID tag. FIG. 4 is a side view of the coupling portion and the coupling module in the RFID tag as viewed in a direction parallel to the winding axis of the coupling portion. FIG. 5 is a perspective view showing the inside of the coupling module in the RFID tag. FIG. 6 is a transparent plan view of the inside of the coupling module in the RFID tag. FIG. 7 is a diagram showing antenna gain-frequency characteristics of the RFID tag according to the first embodiment and the RFID tags according to the first and second comparative examples. Fig. 8A is a perspective view of a tire equipped with an RFID tag according to embodiment 1. Fig. 8B is a front view of a main part of the tire equipped with the RFID tag. FIG. 9 is an explanatory diagram of the positional relationship between a first end and a second end of the coupling portion when the coupling portion is viewed from a direction parallel to the winding axis of the coupling portion, with respect to the spring antenna in the RFID tag described above. FIG. 10 is a perspective view of an RFID tag according to the second embodiment. FIG. 11 is a perspective view of an RFID tag according to the third embodiment. FIG. 12 is a front view of the RFID tag.

Embodiments 1 to 3 are described below with reference to the drawings. The drawings referred to in the following embodiments 1 to 3 are schematic drawings, and the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensions, and the size and thickness ratios between the components do not necessarily reflect the actual dimensional ratios.

(Embodiment 1)
1 and 2, an RFID tag 1 according to the first embodiment includes a spring antenna 2 and a coupling module 3. The coupling module 3 is, for example, a module that magnetically couples with the spring antenna 2. In the RFID tag 1, the coupling module 3 and the spring antenna 2 are magnetically coupled.

The RFID tag 1 is embedded in a tire casing 101 of a tire 100, for example, as shown in Figures 8A and 8B. The RFID tag 1 communicates with, for example, an external reader device.

5 and 6, the coupling module 3 is, for example, a rectangular parallelepiped that is elongated in a first direction D31. The coupling module 3 is a rectangular parallelepiped whose length in the first direction D31 is longer than its length in a second direction D32 perpendicular to the first direction D31.

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 that magnetically couples with the spring antenna 2. The helical antenna 6 is a magnetic field coupling element with the spring antenna 2, and is also an element for the matching circuit of the RFIC element 7 in the coupling module 3.

The coupling module 3 has a printed wiring board 30, a resin block 31, and a protective layer 32. The helical antenna 6 of the coupling module 3 includes two conductor parts 61a, a plurality (12 in the example of FIG. 5) of first connection conductor parts 61b and one intermediate conductor part 61c, a plurality (28 in the example of FIG. 5), and a plurality (14 in the example of FIG. 5) of second connection conductor parts 63, which are included in the printed wiring board 30. The plurality of metal pins 62 are arranged on the printed wiring board 30. More specifically, two of the 28 metal pins 62 are arranged on the two conductor parts 61a, each of the 24 metal pins 62 is arranged on the first end or the second end of any one of the plurality of first connection conductor parts 61b, one metal pin 62 is arranged on the first end of the intermediate conductor part 61c, and one metal pin 62 is arranged on the second end of the intermediate conductor part 61c. The RFIC element 7 is disposed, for example, on the printed wiring board 30. The resin block 31 is disposed on the printed wiring board 30, and covers the side surfaces of each of the multiple metal pins 62 and the RFIC element 7. Each of the multiple second connection conductors 63 is disposed across two metal pins 62 aligned along a second direction D32 perpendicular to the first direction D31 in a plan view from the thickness direction D30 of the printed wiring board 30. The protective layer 32 is disposed on the resin block 31, and covers the multiple second connection conductors 63.

The material of each of the two conductor parts 61a, the multiple first connecting conductor parts 61b, and the intermediate conductor part 61c includes, for example, copper. The material of each of the multiple metal pins 62 includes, for example, copper or a copper alloy. Furthermore, the material of each of the multiple second connecting conductor parts 63 includes, for example, copper.

The material of the resin block 31 includes a resin (e.g., epoxy resin). The material of the protective layer 32 includes, for example, a resin (e.g., epoxy resin, polyimide, etc.).

The external shape of the coupling module 3 is composed of the printed wiring board 30, the resin block 31, and the protective layer 32, and is a rectangle when viewed from the first direction D31 parallel to the winding axis A6 of the helical antenna 6 (see Figs. 4 and 5). In the RFID tag 1, the length of the diagonal in the external shape of the coupling module 3 viewed from the first direction D31 may be shortened, and the gap between the helical antenna 6 and the spring antenna 2 may be narrowed, thereby strengthening the magnetic field coupling between the helical antenna 6 and the spring antenna 2. Specifically, in order to shorten the length of the diagonal, the corners of only the resin block 31 may be cut to make the external shape of the coupling module 3 viewed from the first direction D31, for example, a hexagon, or the printed wiring board 30 may also be cut to make it an octagon, and the gap between the helical antenna 6 and the spring antenna 2 may be narrowed. When shortening the length of the diagonal in the external shape of the coupling module 3 viewed from the first direction D31, the entire coupling module 3 may be chamfered, for example, by barrel polishing.

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

The RFIC element 7 is connected between the first end 611 and the second end 612 of the helical antenna 6. The RFIC element 7 is, for example, an RFIC chip. In this embodiment, the 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 the RFIC element 7 is connected to the first land electrode 33 of the printed wiring board 30. The second input/output terminal of the RFIC element 7 is connected to the second land electrode 34 of the printed wiring board 30. As a result, the RFIC element 7 is connected to the first end 611 of the helical antenna 6 via the first wiring part 35 of the printed wiring board 30, and is connected to the second end 612 of the helical antenna 6 via the second wiring part 36 of the printed wiring board 30. Therefore, in the coupling module 3, an inductor formed by the helical antenna 6 is connected between the first input/output terminal and the second input/output terminal of the RFIC element 7.

(1.2) Spring Antenna The spring antenna 2 will now be described with reference to FIGS.

The spring antenna 2 is an antenna that functions as a radio wave emitter from the RFID tag 1, and functions as an antenna booster. The spring antenna 2 is elastically deformable. The spring antenna 2 includes a 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).

The free length of the spring antenna 2 is determined based on half the wavelength of the radio waves communicated by the RFID tag 1. The communication frequency band of the RFID tag 1 is, for example, the UHF band, and as an example, is 860 MHz to 920 MHz. The length of the spring antenna 2 is, for example, 60 mm.

As shown in Figures 1 and 3, the spring antenna 2 has a helical coupling portion 20, a first helical radiating portion 21, a second helical radiating portion 22, a first intermediate portion 23, and a second intermediate portion 24.

When 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 aligned 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.

The coupling module 3 is disposed on the inside of the coupling section 20. That is, in the spring antenna 2, the coupling module 3 is disposed on the inside of the coupling section 20. In the spring antenna 2, the coupling module 3 is disposed on the winding axis A20 of the coupling section 20. The winding axis A20 of the coupling section 20 is parallel to the winding axis A6 of the helical antenna 6 (see Figures 5 and 6). "The winding axis A20 of the coupling section 20 is parallel to the winding axis A6 of the helical antenna 6" does not only mean strictly parallel, but also includes cases where the acute angle between the winding axis A20 of the coupling section 20 and the winding axis A6 of the helical antenna 6 is 10 degrees or less.

As shown in FIG. 2, the coupling portion 20 has a first end 201 and a second end 202. In this embodiment, as shown in FIG. 4, the second end 202 of the coupling portion 20 overlaps the coupling module 3 when viewed from a direction D1 parallel to the winding axis A20 of the coupling portion 20. 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 shown in FIG. 4, it becomes easier to fix the coupling module 3 in the coupling portion 20 when the coupling module 3 is inserted into the coupling portion 20. For example, the RFID tag 1 of this embodiment may be constructed by inserting the coupling module 3 into the coupling portion 20 from the first end 201 of the coupling portion 20 and fixing the coupling module 3 to the coupling portion 20 with an adhesive (not shown) made of a flexible resin material, for example a silicone rubber-based resin material. In this embodiment, the second end 202 of the coupling part 20 overlaps the coupling module 3 when viewed from the direction D1 parallel to the winding axis A20 of the coupling part 20, but instead of the second end 202, the first end 201 may overlap the coupling module 3 when viewed from the direction D1 parallel to the winding axis A20 of the coupling part 20.

As shown in FIG. 1, the winding direction D20 of the coupling portion 20 is a clockwise direction when viewed from a direction D1 parallel to the winding axis A20, and is the same as the winding direction (clockwise direction) of the helical antenna 6.

As shown in FIG. 3, in a direction D1 parallel to the winding axis A20 of the coupling portion 20, the length H20 of the coupling portion 20 is longer than the length H3 of the coupling module 3, but may be less than or equal to the length H3 of the coupling module 3.

In addition, in this embodiment, in the direction D1 parallel to the winding axis A20 of the coupling portion 20, the length H20 of the coupling portion 20 is shorter than each of the length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22, but may be the same length as each of the length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22. Each of the electrical length of the helical first radiating portion 21 and the electrical length of the helical second radiating portion 22 is determined based on the half wavelength of the radio waves communicated by the RFID tag 1.

In the first embodiment, 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 the same. "The length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22 are the same" means that the length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22 do not have to be exactly the same. "The length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22 are the same" includes cases where the length H21 of the first radiating portion 21 is 90% or more and 110% or less of the length H22 of the second radiating portion 22.

In this embodiment, as shown in FIG. 1, when viewed from a direction D1 parallel to the winding axis A20 of the coupling portion 20, the winding direction D21 of the first radiating portion 21 is opposite to the winding direction D20 of the coupling portion 20. Also, when viewed from a direction D1 parallel to the winding axis A20 of the coupling portion 20, the winding direction D22 of the second radiating portion 22 is opposite to the winding direction D20 of the coupling portion 20.

3, in the direction D1 parallel to the winding axis A20 of the coupling unit 20, the length H23 of the first intermediate portion 23 is longer than the length H3 of the coupling module 3, but may be the same as the length H3 of the coupling module 3. The first intermediate portion 23 has less than one turn per length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling unit 20, and is located between the coupling unit 20 and the first radiating portion 21. "The first intermediate portion 23 has less than one turn per length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling unit 20" means that the number of turns of the first intermediate portion 23 is less than one in the range of the same length as the length H3 of the coupling module 3. Even if the first intermediate portion 23 has a twisted shape in the range of the same length as the length H3 of the coupling module 3, the number of turns is less than one. In the first embodiment, the first intermediate portion 23 has a linear shape and has zero turns per length H3 of the coupling module 3 in a direction D1 parallel to the winding axis A20 of the coupling portion 20. The first intermediate portion 23 is located on the winding axis A20 of the coupling portion 20. In the first embodiment, the first intermediate portion 23 constitutes a first connection portion that connects the coupling portion 20 and the first radiation portion 21.

In the direction D1 parallel to the winding axis A20 of the coupling portion 20, the length H24 of the second intermediate portion 24 is longer than the length H3 of the coupling module 3, but may be the same as the length H3 of the coupling module 3. The second intermediate portion 24 has less than one turn per length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20, and is located between the coupling portion 20 and the second radiation portion 22. "The second intermediate portion 24 has less than one turn per length H3 of the coupling module 3 in the direction D1 parallel to the winding axis A20 of the coupling portion 20" means that the number of turns of the second intermediate portion 24 is less than one in the range of the same length as the length H3 of the coupling module 3. Even if the second intermediate portion 24 has a twisted shape in the range of the same length as the length H3 of the coupling module 3, the number of turns is less than one. In the first embodiment, the second intermediate portion 24 has a linear shape and has zero turns per length H3 of the coupling module 3 in a direction D1 parallel to the winding axis A20 of the coupling portion 20. The second intermediate portion 24 is located on the winding axis A20 of the coupling portion 20. In the first embodiment, the second intermediate portion 24 constitutes a second connection portion that connects the coupling portion 20 and the second radiation portion 22.

In the first embodiment, in the direction D1 parallel to the winding axis A20 of the joint portion 20, the length H23 of the first intermediate portion 23 and the length H24 of the second intermediate portion 24 are the same. "The length H23 of the first intermediate portion 23 and the length H24 of the second intermediate portion 24 are the same" does not mean that the length H23 of the first intermediate portion 23 and the length H24 of the second intermediate portion 24 are strictly the same. "The length H23 of the first intermediate portion 23 and the length H24 of the second intermediate portion 24 are the same" includes cases where the length H23 of the first intermediate portion 23 is 80% or more and 120% or less of the length H24 of the second intermediate portion 24.

(2) Method for Manufacturing RFID Tag In a method for manufacturing the RFID tag 1, a first step of preparing the spring antenna 2 and a second step of arranging the coupling module 3 inside the coupling portion 20 of the spring antenna 2 are carried out in sequence.

In the first step, for example, a spring antenna 2 is prepared by forming a steel wire (e.g., piano wire or stainless steel wire) and then heat-treating it at a predetermined temperature (e.g., 400° C.). In the spring antenna 2 which has been heat-treated at the predetermined temperature after forming, the stress generated during the spring deformation process of the steel wire is released, so that the dimensional accuracy of each of the joint 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, and an oxide coating containing Fe ₃ O ₄ is formed on the surface of the steel wire.

In the second step, the coupling module 3 is inserted into the inside of the coupling portion 20 of the spring antenna 2, which 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, in a direction along the winding axis A20 of the coupling portion 20 (direction D1), from the first intermediate portion 23 side (or the second intermediate portion 24 side), and the coupling module 3 is fixed to the spring antenna 2. When coupling the coupling module 3 to the spring antenna 2, for example, the coupling portion 20 and the coupling module 3 may be molded with resin or rubber, or the spring antenna 2 and the coupling module 3 may be fixed with an adhesive. Alternatively, a part of the spring antenna 2 may be bent to prevent the coupling module 3 from coming off the coupling portion 20.

In the manufacturing method of the RFID tag 1 of this embodiment, the first and second steps can be performed separately, so compared to a manufacturing method in which a coupling module is placed while the steel wire is being processed into a spring and a spring is formed around the coupling module, the dimensional accuracy of the spring antenna 2 is improved and it is possible to prevent a load from being applied to the coupling module 3 when the coupling module 3 is inserted. This makes the coupling module 3 less likely to be damaged, making it possible to improve manufacturing quality.

(3) Operation of RFID Tag In RFID tag 1, when spring antenna 2 receives radio waves (signals) in the UHF communication frequency band, the radio waves are transmitted to helical antenna 6 that is magnetically coupled to spring antenna 2, and a current corresponding to the signal flows in RFIC element 7. RFIC element 7 operates by receiving the current supplied from helical antenna 6, and outputs a current (signal) corresponding to information stored in a memory unit (not shown) inside RFIC element 7 to helical antenna 6. The radio waves (signals) corresponding to this current are radiated to the outside from spring antenna 2 that is magnetically coupled to helical antenna 6.

The spring antenna 2 in the RFID tag 1 of embodiment 1 has a first intermediate portion 23 between the connecting portion 20 and the first radiating portion 21, and a second intermediate portion 24 between the connecting portion 20 and the second radiating portion 22, so it functions like an antenna with a dipole structure.

(4) Antenna gain-frequency characteristics of RFID tags Fig. 7 shows the antenna gain-frequency characteristics of the RFID tag 1 of one example of embodiment 1, the RFID tag of comparative example 1, and the RFID tag of comparative example 2. "G1" in Fig. 7 shows the antenna gain-frequency characteristics of the RFID tag 1 of one example, "R1" in Fig. 7 shows the antenna gain-frequency characteristics of the RFID tag of comparative example 1, and "R2" in Fig. 7 shows the antenna gain-frequency characteristics of the RFID tag of comparative example 2.

In the RFID tag of Comparative Example 1, the total length (free length) of the spring antenna is 60 mm, and the pitch of the spring constituting the spring antenna is larger than the pitch of the helical joint 20 of the first embodiment. In the RFID tag of Comparative Example 2, the total length (free length) of the spring antenna is 37 mm, and the pitch of the spring constituting the spring antenna is larger than the pitch of the helical joint 20 of the first embodiment. In the RFID tag of Comparative Example 1, the pitch of the spring constituting the spring antenna is the same as the inner diameter of the spring constituting the spring antenna. In the RFID tag of Comparative Example 2, the pitch of the spring constituting the spring antenna is also the same as the pitch of the spring constituting the spring antenna in the RFID tag of Comparative Example 1. The inner diameter of the spring-shaped joint 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.

As can be seen from Figure 7, the RFID tag of Comparative Example 1 has an improved antenna gain compared to the RFID tag of Comparative Example 2. In Figure 7, for "R1" showing the antenna gain-frequency characteristics of Comparative Example 1, the resonance peak of the coupling module appears near 0.90 GHz, but the peak of the spring antenna appears at a frequency higher than 1.10 GHz (near 1.3 GHz) (not shown). For "R2" showing the antenna gain-frequency characteristics of Comparative Example 2, the resonance peak of the coupling module appears near 0.90 GHz, but the resonance peak of the spring antenna appears near 1.2 GHz (not shown).

As can be seen from FIG. 7, the RFID tag 1 of one embodiment has an improved antenna gain compared to Comparative Example 1. Furthermore, in "G1" showing the antenna gain-frequency characteristics of the RFID tag 1 of one embodiment, the resonance peak of the coupling module 3 appears near 0.90 GHz, and the resonance peak of the spring antenna 2 appears near 0.96 GHz. In other words, from FIG. 7, it can be seen that in one embodiment, compared to Comparative Example 1, the coupling coefficient between the coupling module 3 and the spring antenna 2 can be made smaller without making the inner diameter of the coupling portion 20 of the spring antenna 2 larger than the inner diameter of the spring antenna of Comparative Example 1. From the above, it can be seen that the RFID tag 1 of one embodiment can improve the antenna gain in the communication frequency band by the RFID tag 1.

(5) Tire Structure As shown in Fig. 8A and Fig. 8B , the tire 100 according to the first embodiment includes an RFID tag 1 and a tire casing 101 in which the RFID tag 1 is embedded. The tire 100 further includes a wheel 104. The tire 100 is, for example, a tire used on a vehicle such as an automobile.

The tire casing 101 includes an electrically insulating elastomer. An elastomer is a polymeric substance that has rubber-like elasticity at room temperature. The term "elastomer" includes, for example, diene polymers, i.e., polymers containing diene units, silicone, polyurethane, polyolefin, and other thermoplastic elastomers. The tire casing 101 includes a tread 102 and a sidewall 103. The RFID tag 1 is embedded in the sidewall 103 of the tire casing 101. In particular, when the RFID tag 1 is embedded in the sidewall 103, the sidewall 103 has metal fibers arranged radially (radially), and therefore, in order to reduce deterioration of the antenna radiation characteristics due to the influence of the metal fibers, the RFID tag 1 is arranged perpendicular to the metal fibers. The RFID tag 1 may be enclosed, for example, between two layers of electrically insulating rubber that has a high affinity with the elastomer in the sidewall 103, or between two layers of elastomer.

(6) Effects In the RFID tag 1 according to the first embodiment, the spring antenna 2 has a helical coupling portion 20, a first helical radiating portion 21, a second helical radiating portion 22, a first intermediate portion 23, and a second intermediate portion 24. The first intermediate portion 23 has less than one turn per length H3 of the coupling module 3 in a direction D1 parallel to the winding axis A20 of the coupling portion 20, and is located between the coupling portion 20 and the first radiating portion 21. The second intermediate portion 24 has less than one turn per length H3 of the coupling module 3 in a direction D1 parallel to the winding axis A20 of the coupling portion 20, and is located between the coupling portion 20 and the second radiating portion 22.

The above configuration makes it possible to improve the antenna gain. More specifically, in the RFID tag 1 according to embodiment 1, the current generated in the coupling part 20 due to the magnetic field coupling between the coupling part 20 and the helical antenna 6 of the coupling module 3 is less likely to be radiated to the outside as magnetic field energy in the first intermediate part 23 and the second intermediate part 24, and is efficiently transmitted to the first helical radiation part 21 and the second helical radiation part 22, thereby making it possible to improve the antenna radiation efficiency and the antenna gain.

Furthermore, in the RFID tag 1 according to embodiment 1, 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.

The above configuration may reduce the effect of magnetization when the coupling portion 20, the first radiating portion 21, and the second radiating portion 22 are magnetized, causing a change in the inductance of the spring antenna 2 and a change in the resonant frequency of the spring antenna 2, resulting in a phenomenon of wavelength shortening. If the effect 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 may be the same as the winding direction D20 of the coupling portion 20.

The tire 100 of the first embodiment includes an RFID tag 1 and a tire casing 101 in which the RFID tag 1 is embedded.

The above configuration makes it possible to improve antenna gain.

(Modification of the first embodiment)
In a modified example of embodiment 1, when viewed from a direction D1 (see FIG. 1) parallel to the winding axis A20 of the joint 20, as shown in FIG. 9, an angle θ1 between a straight line SL1 passing through the winding axis A20 of the joint 20 and the first end 201 of the joint 20 and a straight line SL2 passing through the winding axis A20 of the joint 20 and the second end 202 of the joint 20 is 90 degrees or less.

The above configuration allows the spring antenna 2 to be stably positioned on the jig or stage on which the spring antenna 2 is placed during the manufacture of the RFID tag 1, making it easier to insert the coupling module 3 inside the coupling portion 20 of the spring antenna 2 and to position the coupling module 3 relative to the coupling portion 20.

The modified example of the first embodiment can improve the antenna gain, similar to the RFID tag 1 of the first embodiment.

(Embodiment 2)
An RFID tag 1A according to the second embodiment will be described with reference to Fig. 10. Regarding the RFID tag 1A according to the second embodiment, the same components as those of the RFID tag 1 according to the first embodiment (see Figs. 1 to 7, 8A and 8B) are denoted by the same reference numerals and description thereof will be omitted.

(1) Configuration The RFID tag 1A according to the second embodiment differs from the RFID tag 1 according to the first embodiment in that the winding axis A21 of the first radiating portion 21 and the winding axis A22 of the second radiating portion 22 are misaligned with the winding axis A20 of the coupling portion 20 in a direction perpendicular to the direction D1 parallel to the winding axis A20 of the coupling portion 20.

In this embodiment, when viewed from a direction D1 parallel to the winding axis A20 of the coupling portion 20, the winding direction (winding direction) D20 of the coupling portion 20 is a clockwise direction (right-handed winding), and the winding direction D21 of the first radiating portion 21 is a counterclockwise direction (left-handed winding). In this 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.

(2) Effects As with the RFID tag 1 according to embodiment 1, the RFID tag 1A according to embodiment 2 has a spring antenna 2 that includes a helical coupling portion 20, a first helical radiating portion 21, a second helical radiating portion 22, a first intermediate portion 23, and a second intermediate portion 24, and therefore can improve antenna gain. Also, in the RFID tag 1A according to embodiment 2, it is easy to arrange the coupling module 3 inside the coupling portion 20.

In addition, in the RFID tag 1A according to embodiment 2, the winding axis A21 of the first radiating portion 21 and the winding axis A22 of the second radiating portion 22 are misaligned with the winding axis A20 of the coupling portion 20 in a direction perpendicular to the direction D1 parallel to the winding axis A20 of the coupling portion 20.

With the above configuration, when manufacturing the RFID tag 1A, the first radiating portion 21 and the second radiating portion 22 are unlikely to get in the way when inserting the coupling module 3 into the coupling portion 20, making it easier to insert the coupling module 3 into the coupling portion 20.

Furthermore, in the RFID tag 1A according to embodiment 2, 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.

The above configuration may reduce the effect of magnetization when each of the coupling portion 20, the first radiating portion 21, and the second radiating portion 22 is magnetized, causing a change in the inductance of the spring antenna 2 and a change in the resonant frequency of the spring antenna 2, resulting in a phenomenon of wavelength shortening. If the effect 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 may be the same as the winding direction D20 of the coupling portion 20.

(Embodiment 3)
An RFID tag 1B according to the third embodiment will be described with reference to Fig. 11 and Fig. 12. Regarding the RFID tag 1B according to the third embodiment, the same components as those of the RFID tag 1 according to the first embodiment (see Figs. 1 to 7, 8A and 8B) are denoted by the same reference numerals and description thereof will be omitted.

(1) Configuration 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.

(2) Effects The RFID tag 1B according to the third embodiment can improve the antenna gain, similarly to the RFID tag 1 according to the first embodiment. Furthermore, in the RFID tag 1B according to the third embodiment, when 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 between the length H21 of the first radiating portion 21 and the length H22 of the second radiating portion 22.

The above-mentioned embodiments 1 to 3 are merely one of various embodiments of the present invention. The above-mentioned embodiments 1 to 3 can be modified in various ways depending on the design, etc., and can be combined as appropriate, as long as the object of the present invention can be achieved.

(Other Modifications)
For example, the structure of the coupling module 3 is not limited to the examples shown in FIGS. 5 and 6, and may have other structures.

The products to which the RFID tag 1 is applied are not limited to tires 100, but may also include, for example, clothing, linens, etc.

(Aspects)
The present specification discloses the following aspects.

The RFID tag (1; 1A; 1B) according to the first aspect includes a spring antenna (2) and a coupling module (3). The coupling module (3) includes a helical antenna (6) and an RFIC element (7). The RFIC element (7) is connected to the helical antenna (6). The spring antenna (2) includes a helical coupling portion (20), a first helical radiating portion (21), a second helical radiating portion (22), a first intermediate portion (23), and a second intermediate portion (24). The coupling portion (20) has the coupling module (3) disposed inside. The first intermediate portion (23) has less than one turn per length (H3) of the coupling module (3) in a direction (D1) parallel to the winding axis (A20) of the coupling portion (20), and is located between the coupling portion (20) and the first radiating portion (21). The second intermediate portion (24) has less than one turn per length (H3) of the coupling module (3) in a direction (D1) parallel to the winding axis (A20) of the coupling portion (20), and is located between the coupling portion (20) and the second radiating portion (22).

This aspect makes it possible to improve antenna gain.

In the RFID tag (1; 1A; 1B) according to the second embodiment, in the first embodiment, in a 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 each longer than the length (H3) of the coupling module (3).

According to this embodiment, during manufacturing, it is possible to easily position the coupling module (3) inside the coupling portion (20) of the spring antenna (2), thereby improving the performance of the spring antenna (2).

In the RFID tag (1A) according to the third aspect, in the first or second aspect, the winding axis (A21) of the first radiating portion (21) and the winding axis (A22) of the second radiating portion (22) are misaligned with the winding axis (A20) of the connecting portion (20) in a direction perpendicular to a direction (D1) parallel to the winding axis (A20) of the connecting portion (20).

This embodiment makes it easier to insert the connection module (3) inside the connection portion (20) during manufacturing.

In the RFID tag (1; 1A; 1B) according to the fourth aspect, in any one of the first to third aspects, 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 connecting portion (20).

According to this embodiment, when the coupling portion (20), the first radiation portion (21), and the second radiation portion (22) are magnetized and the magnetic susceptibility increases, the inductance of the spring antenna (2) changes, the resonant frequency of the spring antenna (2) changes, and a phenomenon of wavelength shortening occurs, the effect of magnetization may be offset.

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

According to this embodiment, it is possible to reduce the coupling coefficient between the coupling portion (20) and the helical antenna (6), thereby weakening the magnetic coupling.

In the RFID tag (1; 1A; 1B) according to the sixth aspect, in any one of the first to fifth aspects, 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 with the coupling module (3) when viewed from a direction (D1) parallel to the winding axis (A20) of the coupling portion (20).

According to this embodiment, when the coupling module (3) is easily placed inside the coupling portion (20) of the spring antenna (2) during manufacturing, the positioning of the coupling module (3) becomes easy and it becomes possible to prevent the coupling module (3) from falling off the coupling portion (20).

In the RFID tag (1; 1A; 1B) according to the seventh aspect, in any one of the first to sixth aspects, the spring antenna (2) includes piano wire or stainless steel wire.

This embodiment makes it possible to improve the durability of the spring antenna (2).

In the RFID tag (1; 1A; 1B) according to the eighth aspect, in the seventh aspect, the material of the spring antenna (2) contains Fe ₃ O ₄ .

This aspect makes it possible to improve reliability.

The tire (100) according to the ninth aspect includes an RFID tag (1; 1A; 1B) according to any one of the first to eighth aspects, and a tire casing (101) in which the RFID tag (1; 1A; 1B) is embedded.

This aspect makes it possible to improve antenna gain.

In the tire (100) according to the tenth aspect, in the ninth aspect, the tire casing (101) includes an electrically insulating elastomer.

In the tire (100) according to the eleventh aspect, in the tenth aspect, the tire casing (101) has a sidewall (103). The RFID tag (1; 1A; 1B) is embedded in the sidewall (103) of the tire casing (101).

According to this aspect, the RFID tag (1; 1A; 1B) is less susceptible to external forces while the vehicle equipped with the tire (100) is traveling, making it possible to improve the reliability of the RFID tag (1; 1A; 1B).

1, 1A, 1B RFID tag 2 Spring antenna 20 Coupling portion 201 First end 202 Second end 21 First radiating portion 22 Second radiating portion 23 First intermediate portion 24 Second intermediate portion 3 Coupling module 6 Helical antenna 7 RFIC element 100 Tire 101 Tire casing 103 Sidewall A6 Winding axis A20 Winding axis A21 Winding axis A22 Winding axis D1 Direction D20 Winding direction D21 Winding direction D22 Winding direction D31 First direction D32 Second direction H3 Length H20 Length H21 Length H22 Length H23 Length H24 Length

Claims (11)

A spring antenna,
a coupling module;
The binding module comprises:
A helical antenna,
an RFIC element connected to the helical antenna;
The spring antenna is
a helical coupling part, the coupling module being disposed inside the helical coupling part;
A helical first radiating portion;
A helical second radiating portion;
a first intermediate portion having less than one turn per length of the coupling module in a direction parallel to the winding axis of the coupling portion and located between the coupling portion and the first radiating portion;
a second intermediate portion having less than one turn per length of the coupling module in the direction parallel to the winding axis of the coupling portion and located between the coupling portion and the second radiating portion;
RFID tag. In the direction parallel to the winding axis of the coupling portion, a length of the first intermediate portion and a length of the second intermediate portion are each longer than a length of the coupling module.
The RFID tag of claim 1 . a winding axis of the first radiating portion and a winding axis of the second radiating portion are offset from the winding axis of the coupling portion in a direction perpendicular to the direction parallel to the winding axis of the coupling portion.
The RFID tag according to claim 1 or 2. a winding direction of the first radiating portion and a winding direction of the second radiating portion are opposite to a winding direction of the coupling portion;
The RFID tag according to any one of claims 1 to 3. In the direction parallel to the winding axis of the coupling portion, a length of the coupling portion is shorter than each of a length of the first radiating portion and a length of the second radiating portion.
The RFID tag according to any one of claims 1 to 4. 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 from the direction parallel to the winding axis of the coupling portion.
The RFID tag according to any one of claims 1 to 5. The spring antenna comprises a piano wire or a stainless steel wire.
The RFID tag according to any one of claims 1 to 6. The material of the spring antenna includes _{Fe3O4 ;}
The RFID tag according to claim 7. An RFID tag according to any one of claims 1 to 8;
and a tire casing having the RFID tag embedded therein.
tire. The tire casing includes an electrically insulating elastomer.
10. The tire of claim 9. The tire casing has a sidewall,
The RFID tag is embedded in the sidewall of the tire casing.
11. The tire of claim 10.

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