Radio frequency identification (RFID) device to be inserted into a tire

Abstract

A tyre comprising a tread, a carcass defining an inner cavity, an inner liner designed to ensure that the air contained in the inner cavity is maintained under pressure, and a radiofrequency identification device fixed on a free surface of the inner liner. The radiofrequency identification device comprises a transmission assembly (1) comprising at least an RFID chip (2) and an antenna (3) connected to the RFID chip (2), and a rubber covering structure covering the transmission assembly (1) and fixed on the free surface of the inner liner. The rubber covering structure has a stress relaxation modulus (G m (0))cs which is less than the stress relaxation modulus (Gm(0))i of the inner liner.

Description

Technical Field

[0001] This invention relates to a radio frequency identification (RFID) device to be inserted into a tire. Background Technology

[0002] In the tire industry, manufacturers have expressed a need for solutions that can automatically and clearly identify tires during production, use, and disposal.

[0003] For example, in tire production, automatic and clear tire identification enables manufacturers to optimize production processes and logistics operations, support the use of automated control systems, and perform effective tire positioning / tracking, thereby establishing a smart tire factory.

[0004] In this regard, the use of radio frequency identification (RFID) devices applied to the outer surface of the inner lining is known. The device comprises a rubber covering structure and a transmission assembly, which includes at least an RFID chip and an antenna connected to the chip, the transmission assembly being arranged inside the covering structure.

[0005] The overlay structure may include a single layer or several layers. For example, the overlay structure may consist of a single layer with a cylindrical construction, in which the transmission components are integrated inside the single layer, or it may consist of a pair of layers arranged in a sandwich-like manner to accommodate the transmission components.

[0006] The aforementioned device is susceptible to drawbacks caused by the stresses experienced by the antenna during tire use. These stresses result from the deformation of the device as a whole and consequently the antenna, each time the tire rotates and presses against the ground in the area of ​​the device. These continuous and repetitive stresses can lead to antenna degradation or separation of the antenna from the coverage structure. Summary of the Invention

[0007] The inventors of this invention investigated how the stress applied to the antenna relates to the mechanical properties of the antenna and the rubber covering structure.

[0008] Following these studies, the inventors of this invention designed a radio frequency identification (RFID) device, characterized by features such as minimizing the stress on the antenna during tire rotation.

[0009] In particular, the inventors of this invention focused their attention on the viscoelastic properties of the rubber-coated structure. In effect, stress is transferred from the liner to the antenna through the rubber-coated structure.

[0010] Here is the equation for the distribution of stress (σ) along the x-coordinate of the antenna at the moment of applied deformation. The x-coordinate represents the distance of a point on the antenna from the center of the antenna.

[0011]

[0012] Where Ef is the antenna stiffness, r i The value represents the radius of the antenna, and ε0 represents the degree of deformation at time 0. The subscript "0" after each value indicates that the time is 0, i.e., the value is related to the time when the deformation occurs.

[0013] ζ and β0 are defined as follows:

[0014] ζ=L / 2r i

[0015] β0=2G m (0) / E f ln(R / r i )

[0016] Where L represents the length of the antenna, G m (0) is the stress relaxation modulus of the rubber cover and R is the radius of the cover.

[0017] The following description will begin with the assumption that the stiffness of the antenna is expressed by an elastic modulus greater than 10 MPa. However, in general, antennas considered suitable for the device according to the invention have an elastic modulus in the range of 15 MPa to 25 MPa.

[0018] Based on the equations shown below, the inventors of this invention determined the states of the rubber covering layer, such as ensuring that the stress level applied to the antenna does not impair the function of the device as a whole. In this regard, the inventors found that, for the purposes of this invention, evaluating the relationship between the stress relaxation modulus of the rubber covering layer and the inner liner to which the RFID device is fixed is relevant. Indeed, as mentioned above, stress is transmitted from the inner liner to the antenna through the rubber covering layer. Therefore, to ensure a low stress level applied to the antenna during tire use, the stress relaxation modulus of the rubber covering structure needs to be smaller than that of the inner liner.

[0019] The subject of this invention is a tire comprising a tread, a carcass defining an inner cavity, an inner liner designed to ensure that air contained within the inner cavity is kept under pressure, and a radio frequency identification (RFID) device fixed to a free surface of the inner liner; the RFID device comprising a transmission component and a rubber cover structure, the transmission component comprising at least an RFID chip and an antenna connected to the RFID chip, the rubber cover structure covering the transmission component and fixed to the free surface of the inner liner; the tire is characterized in that the cover structure has a stress relaxation modulus (Gm(0))cs that is less than the stress relaxation modulus (Gm(0))i of the inner liner.

[0020] Preferably, (G) m(0))cs<0.7x(G m (0))i

[0021] The covering structure preferably has a stress relaxation modulus (G) of less than 6 MPa. m (0))cs.

[0022] The antenna preferably has a length in the range of 40 mm to 100 mm; more preferably, it has a length in the range of 40 mm to 60 mm.

[0023] The antenna preferably has an elastic modulus greater than or equal to 10 MPa; more preferably, it has an elastic modulus in the range of 10 MPa to 25 MPa.

[0024] Another subject of the present invention is a radio frequency identification (RFID) device designed to be fixed to a free surface of the inner liner of a tire; the device includes a transmission component and a rubber covering structure, the transmission component including at least an RFID chip and an antenna connected to the RFID chip, the rubber covering structure covering the transmission component; the device is characterized in that the covering structure has a stress relaxation modulus (G) of less than 6 MPa. m (0))cs.

[0025] The state of the antenna (length and elastic modulus) helps to obtain an RFID device that can maintain its function even after the tire has been used and therefore after the device has been subjected to repeated deformation. Attached Figure Description

[0026] Embodiments of the invention will now be described for illustrative and non-limiting purposes with the aid of the accompanying drawings. Figure 1 The transmission component according to the present invention is schematically shown in the figure. Detailed Implementation

[0027] exist Figure 1 The diagram shows a transmission component 1 according to the present invention. The transmission component 1 includes an RFID chip 2 and an antenna 3 connected to the RFID chip 2.

[0028] Three rubber compounds were considered for the production of the cover layer. Each of the cover layers was applied to different transmission components that differed from each other only in the length (L) and elastic modulus (Ef) of antenna 3.

[0029] Specifically, of the three compounds described below, two (A and B) are control compounds and one (C) is a compound according to the invention. One of the two control compounds (A) belongs to the inner liner. This demonstrates that the transmission components of the device cannot be directly bonded to the inside of the inner liner.

[0030] Table I shows the phr composition of the three compounds and the calculated stress relaxation modulus Gm(0) for each compound. The stress relaxation modulus Gm(0) was calculated according to ISO 6914.

[0031] Table I

[0032] Natural rubber -- 100 100 Bromobutyl rubber 100 -- -- Carbon Black N330 -- 50 -- Carbon Black N660 50 -- 50 Calcium carbonate 20 -- -- sulfur 1 5 5 Zinc oxide 3 6 6 MBTS 2 1 1 CBS 0 1 1 6PPD 0.5 0.5 0.5 stearic acid 2 2 2 RAE oil 12 12 12 Gm(0) 7.04 17.62 4.63

[0033] The stress (σ) on the antenna is calculated based on the compound used for the cladding and the type of antenna used. In particular, antennas with different transmission components differ from each other in length (L) and elastic modulus (Ef).

[0034] The covering layer is assumed to be a cylinder, and the antenna is placed inside the cylinder along its axis.

[0035] r i It is assumed to be equal to 1 mm, R is assumed to be equal to 2 mm, and ε0 is assumed to be equal to 15%.

[0036] Table II shows the σ values ​​depending on the cladding compound and the type of antenna. The σ value is calculated near the antenna end; specifically at a distance from the end equal to 5% of the antenna length (L).

[0037] Table II

[0038]

[0039] The values ​​shown in Table II clearly demonstrate that, when the covering layer is manufactured using a compound having the stress relaxation modulus according to the invention, the antenna experiences significantly less stress given the same deformation.

[0040] As will be clearly understood by those skilled in the art, the stress values ​​indicated by the cover layer according to the invention are, for example, to ensure the integrity of the antenna and the stability of the connection between the antenna and the rubber cover layer, and thus to ensure the function of the entire device.

[0041] Conversely, the stresses calculated considering compounds A and B used in the cover layer are too high and cannot ensure the device's function during tire use. In particular, the stress values ​​detected in the cover structure made with liner compound (A) indicate that the transmission assembly cannot be directly inserted into the liner.

[0042] Finally, contrary to the above discussion, the device may include a covering structure that is not composed of a cylindrical rubber layer, but rather of two rubber layers arranged in a sandwich manner and housing the transmission components between them.

Claims

1. A tire comprising a tread, a carcass defining an inner cavity, an inner liner designed to ensure that air contained within the inner cavity is kept under pressure, and a radio frequency identification (RFID) device fixed to a free surface of the inner liner; the RFID device comprising a transmission assembly (1) and a rubber covering structure, the transmission assembly comprising at least an RFID chip (2) and an antenna (3) connected to the RFID chip (2), the rubber covering structure covering the transmission assembly (1) and fixed to the free surface of the inner liner; the tire is characterized in that the rubber covering structure has a stress relaxation modulus (G) smaller than that of the inner liner. m (0))i stress relaxation modulus (G m (0))cs, the rubber covering structure has a stress relaxation modulus (G) of less than 6 MPa. m (0))cs.

2. The tire according to claim 1, characterized in that, (Gm(0))cs<0.7 x(Gm(0))i.

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

4. The tire according to claim 2, characterized in that, The antenna (3) has a length (L) in the range of 40 mm to 100 mm.

5. The tire according to claim 3, characterized in that, The antenna (3) has a length (L) in the range of 40 mm to 60 mm.

6. The tire according to claim 4, characterized in that, The antenna (3) has a length (L) in the range of 40 mm to 60 mm.

7. The tire according to any one of the preceding claims, characterized in that, The antenna (3) has an elastic modulus greater than or equal to 10 MPa.

8. The tire according to claim 7, characterized in that, The antenna (3) has an elastic modulus in the range of 10 MPa to 25 MPa.

9. A radio frequency identification (RFID) device designed to be fixed to a free surface of an inner liner of a tire; the device comprising a transmission component (1) and a rubber covering structure, the transmission component comprising at least an RFID chip (2) and an antenna (3) connected to the RFID chip (2), the rubber covering structure covering the transmission component (1); the device is characterized in that the rubber covering structure has a stress relaxation modulus (G) smaller than that of the inner liner. m (0))i stress relaxation modulus (G m (0))cs, the rubber covering structure has a stress relaxation modulus (G) of less than 6 MPa. m (0))cs.

10. The apparatus according to claim 9, characterized in that, The antenna (3) has a length (L) in the range of 40 mm to 100 mm.

11. The apparatus according to claim 10, characterized in that, The antenna (3) has a length (L) in the range of 40 mm to 60 mm.

12. The apparatus according to any one of claims 9 to 11, characterized in that, The antenna (3) has an elastic modulus greater than or equal to 10 MPa.

13. The apparatus according to claim 12, characterized in that, The antenna (3) has an elastic modulus in the range of 10 MPa to 25 MPa.

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