Radio Frequency Identification (RFID) Device Inserted into a Tire

Abstract

The present invention relates to a tire comprising a tread, a carcass defining an internal cavity, an innerliner layer designed to ensure that the air contained in the internal cavity remains pressurized, and a radio frequency identification device fixed on the free surface of said innerliner layer. The radio frequency identification device includes a transmitting assembly (1) having at least an RFID chip (2) and an antenna (3) connected to the RFID chip (2), and a rubber covering structure covering the transmitting assembly (1) and fixed on the free surface of the innerliner layer. The rubber covering structure is adapted to adjust the stress relaxation rate (G) of the innerliner layer. m (0))i m (0))cs.

Description

Technical Field

[0001] The present invention relates to a radio-frequency identification (RFID) device inserted into a tire.

Background Art

[0002] In the tire industry, manufacturers have expressed the need for a solution that enables automatic and unambiguous identification of tires during manufacturing, use, and disposal.

[0003] For example, particularly with regard to tire manufacturing, automatic and unambiguous identification of tires enables manufacturers to optimize manufacturing processes and logistics operations, support the use of automated control systems, perform efficient location identification / tracking of tires, and thus make it possible to build a smart tire factory.

[0004] In this regard, the use of a radio-frequency identification (RFID) device attached to the outer surface of an innerliner layer is known. This device is composed of a rubber coating structure and a transmission assembly comprising at least an RFID chip and an antenna connected to the chip, and the transmission assembly is disposed inside the coating structure.

[0005] The coating structure may include one single layer or several layers. For example, the coating structure may be composed of one single layer having a cylindrical structure with the transmission assembly incorporated therein, or may be composed of a pair of layers arranged in a sandwich configuration to accommodate the transmission assembly.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The above device is affected by the impairments caused by the stresses received by the antenna during the use of the tire. These stresses are due to the deformation received by the whole device, and thus by the antenna, each time the tire is pressed against the ground within the area of the device by rotation. These continuous and repeated stresses may cause deterioration of the antenna or separation of the antenna from the coating structure.

[0007] The inventors of the present invention have studied how the stress exerted on the antenna is related to the mechanical properties of the antenna and the rubber coating structure.

[0008] Following these studies, the inventors of the present invention have designed a Radio Frequency Identification (RFID) device having technical features that minimize the stress received by the antenna during rotation of the tire.

[0009] In particular, the inventors have focused on the viscoelastic properties of the rubber coating structure. In fact, the stress is transmitted from the inner liner, through the rubber coating structure, to the antenna.

[0010] The following equation provides the distribution of the stress (σ) along the coordinate x of the antenna at the instant when the deformation is applied. The coordinate x represents the distance of a point on the antenna starting from the center of the antenna.

[0011]

Equation

[0012] Here, E f is the stiffness of the antenna, r i is the radius of the antenna, and ε0 indicates the degree of deformation at time 0. The subscript "0" following various quantities indicates the quantity related to time 0, i.e., the instant when the deformation occurs.

[0013] ζ and β0 are defined as shown below. ζ = L / 2r i β0 = 2G m (0) / Ef ln(R / r i )

[0014] Here, L is the length of the antenna, and G m (0) is the stress relaxation rate of the rubber coating layer, and R is the radius of the coating layer.

[0015] The following description starts from the assumption that the rigidity of the antenna is represented by a modulus of elasticity exceeding 10 MPa. However, generally speaking, an antenna considered suitable for the device according to the present invention has a modulus of elasticity within the range of 15 to 25 MPa.

[0016] With the help of the following formula, the inventors of the present invention specified the conditions of the rubber coating layer that ensure the level of stress applied to the antenna without impairing the functionality of the entire device. In this regard, the inventors found that it is relevant to evaluate the relationship between the stress relaxation rate of the rubber coating layer and the inner liner to which the radio frequency identification device is positively fixed for the purpose of the present invention. In fact, as described above, the stress is transmitted from the inner liner through the rubber coating layer to the antenna. Therefore, in order to ensure that the level of stress applied to the antenna during the use of the tire is low, it is necessary to make the stress relaxation rate of the rubber coating structure smaller than the stress relaxation rate of the inner liner.

Means for Solving the Problem

[0017] The gist of the present invention is a tire comprising a tread, a carcass defining an inner cavity, an inner liner layer designed to reliably maintain the air contained in the inner cavity in a pressurized state, and a radio frequency identification device fixed on the free surface of the inner liner layer. The radio frequency identification device includes at least a transmission assembly having an RFID chip and an antenna connected to the RFID chip, and a rubber coating structure covering the transmission assembly and fixed on the free surface of the inner liner layer. The coating structure has a stress relaxation rate (G m (0))i smaller than the stress relaxation rate (G mIt is characterized by having (0))cs.

[0018] Preferably, (G m (0))cs < 0.7×(G m (0))i.

[0019] The covering preferably has a stress relaxation rate (G m (0))cs less than 6 MPa.

[0020] The antenna preferably has a length of 40 to 100 mm, more preferably 40 to 60 mm.

[0021] The antenna preferably has a modulus of elasticity of 10 MPa or more, more preferably 10 to 25 MPa.

[0022] A further subject of the present invention is a radio frequency identification device designed to be fixed on the free surface of the inner liner layer of a tire, the device comprising a transmission assembly including at least an RFID chip and an antenna connected to the RFID chip, and a rubber covering structure covering the transmission assembly, and the device is characterized in that the covering structure has a stress relaxation rate (G m (0))cs less than 6 MPa.

[0023] The conditions of the antenna (length and modulus of elasticity) help to obtain a radio frequency identification device capable of maintaining the functionality of the antenna even after the use of the tire, and thus even after the device has undergone repeated deformations.

[0024] Embodiments of the present invention will be described below for illustrative and non - limiting purposes with reference to the accompanying drawings in which the transmission assembly according to the present invention is shown in schematic form.

Brief Description of the Drawings

[0025]

Figure 1

Modes for Carrying Out the Invention

[0026] The attached drawings show a transmission assembly 1 according to the present invention. The transmission assembly 1 comprises an RFID chip 2 and an antenna 3 connected to the RFID chip 2.

[0027] For the production of the coating layer, three rubber compounds were considered. Each coating layer was applied to different transmission assemblies such that the length (L) and modulus of elasticity (E f ) were different from each other.

[0028] In particular, two of the three compounds described below (A and B) are comparative compounds and one of the three compounds (C) is the compound according to the present invention. One of the two comparative compounds (A) belongs to the inner liner layer. This proves that the transmission assembly of the device cannot be directly incorporated inside the inner liner layer.

[0029] Table I ([Table 1]) shows the phr composition of the three compounds and the calculated values of the stress relaxation rate G m (0) for each compound. The stress relaxation rate G m (0) was calculated according to the ISO6914 standard.

[0030]

Table 1

[0031] The stress (σ) received by the antenna was calculated according to the compound used for the coating layer and according to the type of antenna used. In particular, the antennas of different transmission assemblies have different lengths (L) and moduli of elasticity (E f ).

[0032] It was assumed that the coating layer is a cylinder in which the antenna is arranged along the axis of the cylinder.

[0033] r iAssume that it is equal to 1 mm, assume that R is equal to 2 mm, and assume that ε0 is equal to 15%.

[0034] Table II ([Table 2]) shows the values of σ according to the compound of the coating layer and the type of antenna. The value of σ was calculated in the vicinity of the antenna end, specifically, at a location where the distance from the end is equal to 5% of the antenna length (L).

[0035]

Table 2

[0036] The values shown in Table II clearly show that when the coating layer is manufactured using a compound having a stress relaxation module according to the present invention, the stress received by the antenna is significantly reduced when the same deformation is applied.

[0037] As will be clearly understood by those skilled in the art, the stress values shown for the cover layer according to the present invention ensure the integrity of the antenna and the stability of the connection of the antenna to the rubber cover layer, and as a result, the functionality of the entire device.

[0038] On the contrary, it can be seen that the stress calculated considering Compounds A and B for the coating layer is too high to ensure the functionality of the device during the use of the tire. In particular, the stress value detected in the coating structure manufactured using the inner liner compound (A) indicates that the transmission assembly cannot be directly inserted into the inner liner.

[0039] Finally, in contrast to the above-described, the device may be composed not of a cylindrical rubber layer but of two rubber layers arranged in a sandwich shape, and may include a coating structure that houses the transmission assembly between the two rubber layers.

Claims

1. A tire comprising a tread, a carcass defining an internal cavity, an inner liner layer designed to reliably maintain the air contained in the internal cavity in a pressurized state, and a radio frequency identification device fixed on the free surface of the inner liner layer, wherein the radio frequency identification device includes a transmission assembly (1) having at least an RFID chip (2) and an antenna (3) connected to the RFID chip (2), and a rubber coating structure covering the transmission assembly (1) and fixed on the free surface of the inner liner layer, the rubber coating structure having a stress relaxation rate (Gm(0))cs smaller than the stress relaxation rate (Gm(0))i of the inner liner layer, and (Gm(0))cs < 0.7 × (Gm(0))i.

2. The tire according to claim 1, wherein the coating structure has a stress relaxation rate (Gm(0))cs smaller than 6 MPa.

3. The tire according to claim 1, wherein the antenna (3) has a length (L) of 40 to 100 mm.

4. The tire according to claim 3, wherein the antenna (3) has a length (L) of 40 to 60 mm.

5. The tire according to claim 1, wherein the antenna (3) has a modulus of elasticity (Ef) of 10 MPa or more.

6. The tire according to claim 5, wherein the antenna (3) has a modulus of elasticity (Ef) of 10 to 25 MPa.

7. A radio frequency identification device designed to be fixed on the free surface of the inner liner layer of a tire, the device comprising a transmission assembly (1) including at least an RFID chip (2) and an antenna (3) connected to the RFID chip (2), and a rubber coating structure covering the transmission assembly (1), the device being characterized in that the rubber coating structure has a stress relaxation rate (Gm(0))cs smaller than 6 MPa, and the rubber coating structure has a stress relaxation rate (Gm(0))cs smaller than the stress relaxation rate (Gm(0))i of the inner liner layer.

8. The radio frequency identification device according to claim 7, wherein the antenna (3) has a length (L) of 40 to 100 mm.

9. The radio frequency identification device according to claim 8, wherein the antenna (3) has a length (L) of 40 to 60 mm.

10. The radio frequency identification device according to claim 8 or 9, wherein the antenna (3) has an elastic modulus (Ef) of 10 Mpa or more.

11. The radio frequency identification device according to claim 10, wherein the antenna (3) has an elastic modulus (Ef) of 10 to 25 Mpa.

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