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EP-4377103-B1 - RADIO-FREQUENCY IDENTIFICATION (RFID) DEVICE TO BE INSERTED IN A TYRE

EP4377103B1EP 4377103 B1EP4377103 B1EP 4377103B1EP-4377103-B1

Inventors

  • LOMBARDI, ROBERTO
  • PALUMBI, MARIA CECILIA
  • LIPPIELLO, Guido
  • CAPALDI, Cristian

Dates

Publication Date
20260506
Application Date
20220725

Claims (6)

  1. A tyre comprising a tread, a carcass defining an inner cavity, an innerliner layer designed to make sure that the air contained in the inner cavity remains under pressure, and a radio-frequency identification device, which is fixed on a free surface of said innerliner layer; said radio-frequency identification device comprising a transmission assembly (1) comprising at least a RFID chip (2) and an antenna (3) connected to the RFID chip (2), and a rubber covering structure, which covers said transmission assembly (1) and is fixed on a free surface of said innerliner layer; said tyre being characterized in that said rubber covering structure has a stress relaxation modulus (G m( 0))cs smaller than the stress relaxation modulus (G m ( 0))i of the innerliner layer.
  2. The tyre according to claim 1, characterized in that (Gm(0))cs 〈 0.7 x (Gm(0))i.
  3. The tyre according to one of the previous claims, characterized in that said antenna (3) has a length (L) ranging from 40 to 100 mm.
  4. The tyre according to claim 3, characterized in that said antenna (3) has a length (L) ranging from 40 to 60 mm.
  5. The tyre according to one of the previous claims, characterized in that said antenna (3) has an elastic modulus (Ef) greater than or equal to 10 MPa.
  6. The tyre according to claim 5, characterized in that said antenna (3) has an elastic modulus (Ef) ranging from 10 to 25 MPa.

Description

The invention relates to a radio-frequency identification (RFID) device to be inserted in a tyre. In the tyre industry, manufacturers have expressed the need for solutions that allow for an automated and unequivocal identification of tyres during their production, their use and their disposal. For example, with specific reference to the production of tyres, the automated and unequivocal identification of tyres can allow manufacturers to optimize production processes and logistics operations, support the use of automated control systems, carry out an efficient localization/tracking of the tyres and, hence, build smart tyre factories. To this regard, the use a radio-frequency identification (RFID) device is known, which is applied to the outer surface of the innerliner layer. Said device consists of a rubber covering structure and of a transmission assembly comprising at least a RFID chip and an antenna connected to the chip, said transmission assembly being arranged inside the covering structure. The covering structure can comprise one single layer or several layers. For example, the covering structure can consist of one single layer with a cylindrical conformation with the transmission assembly incorporated on the inside, or it can consist of a pair of layers arranged in a sandwich-like manner so as to contain the transmission assembly. The device described above is affected by a drawback caused by the stresses to which the antenna is subjected during the use of the tyre. These stresses are due to the deformations to which the device as a whole and, hence, also the antenna are subjected every time the tyre, by rotating, is pressed against the ground in the area of the device. These continuous and repeated stresses can cause a deterioration of the antenna or a separation thereof from the covering structure. Prior art devices are described in FR 2 937 284 A1 and US 2004/159383 A1. The inventors of this invention studied how the stress exerted upon the antenna relates to the mechanical properties of the antenna and of the rubber covering structure. Following these studies, the inventors of this invention designed a radio-frequency identification (RFID) device whose technical features are such as to minimize the stresses to which the antenna is subjected during the rotation of the tyre. In particular, the inventors of this invention focused their attention on the viscoelasticity properties of the rubber covering structure. Indeed, stresses are transmitted from the innerliner to the antenna through the rubber covering structure. Here is an equation providing the distribution of the stress (σ) along the coordinate x of the antenna in the moment in which the deformation is applied. The coordinate x represents the distance of a point on the antenna starting from the centre of the antenna. σfx0=Efε01−coshβ0x/ricoshβ0ζ. Wherein Ef is the stiffness of the antenna, ri indicates the radius of the antenna, ε0 indicates the extent of the deformation in the moment 0. The subscript "0" following the different quantities indicates the moment 0, namely the quantity relating to the moment in which the deformation takes place. ζ and β0 are defined as indicated below: ζ=L/2ri β0=2Gm0/EflnR/ri Wherein L indicates the length of the antenna, Gm(0) is the stress relaxation modulus of the rubber covering layer and R is the radius of the covering layer. The description below will start from the assumption that the stiffness of the antenna is expressed by an elastic modulus greater than 10 MPa. However, generally speaking, antennas deemed to be suited for the device according to the invention have an elastic modulus ranging from 15 to 25 MPa. With the support of the equations shown below, the inventors of the invention identified conditions of the rubber covering layer that are such as to ensure a level of stress exerted upon on the antenna that does not compromise the functionality of the device as a whole. To this regard, the inventors found out that, for the purposes of the invention, it is relevant to assess the relationship between the stress relaxation modulus of the rubber covering layer and the one of the innerliner on which the radio-frequency identification device is fixed. Indeed, as mentioned above, stress is transmitted from the innerliner to the antenna through the rubber covering layers. Therefore, in order to ensure low levels of stress exerted upon the antenna during the use of the tyre, the stress relaxation modulus of the rubber covering structure needs to be smaller than the stress relaxation modulus of the innerliner. The subject-matter of the invention is a tyre comprising a tread, a carcass defining an inner cavity, an innerliner layer designed to make sure that the air contained in the inner cavity remains under pressure, and a radio-frequency identification device, which is fixed on a free surface of said innerliner layer; said radio-frequency identification device comprising a transmission assembly comprising