Patent Application
20220348043
The present invention relates to a tyre casing fitted with an electronic radio identification device or radiofrequency transponder which, particularly in service when mounted on a land vehicle, is subjected to severe thermomechanical stresses.
In the field of RFID devices (RFID being the acronym of RadioFrequency IDentification), passive radiofrequency transponders are conventionally used to identify, track and manage objects. These devices allow more reliable and faster automated management.
These passive radiofrequency-identification transponders generally consist of at least one electronic chip and one antenna formed by a magnetic loop or a radiating antenna, which is fastened to the object to be identified.
The communication performance of the radiofrequency transponder is expressed in terms of the maximum distance of communication of the radiofrequency transponder with a radiofrequency reader, for a given signal communicated to or by the radiofrequency reader.
In the case of highly extensible products such as, for example, tyres, there is a need to identify the product throughout its life from its manufacture to its removal from the market and, in particular, during use thereof. Thus, in order to facilitate this task, in particular under the conditions of use on a vehicle, a high communication performance is required, which is expressed in terms of the ability to interrogate the radiofrequency transponder at a large distance (several metres) from the product, via a radiofrequency reader. Lastly, it is desired for the manufacturing cost of such a device to be as competitive as possible.
A passive radiofrequency-identification transponder able to meet the needs of tyres is known in the prior art, and in particular from document WO 2016/193457A1. This transponder consists of an electronic chip, connected to a printed circuit board to which is galvanically connected a first primary antenna. This primary antenna is electromagnetically coupled to a single-strand helical spring that forms a radiating dipole antenna. The communication with an external radiofrequency reader for example uses radiowaves and in particular the UHF band (UHF being the acronym of Ultra-High Frequency). Therefore, the characteristics of the helical spring are adjusted for the chosen communication frequency. Thus, the disappearance of the mechanical junction between the printed circuit board and the radiating antenna improves the mechanical resistance of the radiofrequency transponder.
However, such a passive radiofrequency transponder exhibits weaknesses in its use when incorporated into a tyre casing, in particular when the carcass reinforcement of the tyre casing is made of metal. Although this radiofrequency transponder is suitable for operating at the communication frequency of the external radiofrequency reader, the radiofrequency communication via the radiating antenna is not optimal, in particular for long-distance interrogations, in particular due to the metal reinforcers disturbing the radioelectric waves. In addition, it is also necessary to give consideration to how the radiating antenna will behave mechanically in an environment that is highly stressful thermomechanically. Thus, it is necessary to optimize the performance-related compromise between the mechanical strength of the antenna and its radiocommunication efficacy, such is its radio electric performance and, secondarily, its electromagnetic performance, in order to optimize the potential performance of such a passive radiofrequency transponder.
The present invention relates to a tyre casing having a metal carcass reinforcement, fitted with a passive radiofrequency transponder aimed at improving the performance-related compromise, and in particular the radiocommunication performance of passive radiofrequency transponders used in a tyre design when used on a vehicle.
The invention relates to a tyre casing that is toroidal in shape about a reference axis and equipped with a passive radiofrequency transponder. The tyre casing comprises:
Here, the term “elastomer” is understood to mean all the elastomers including TPEs (acronym of ThermoPlastic Elastomers), such as for example diene polymers, i.e. polymers comprising diene units, silicones, polyurethanes and polyolefins.
Here, the term “electromagnetic coupling” is understood to mean coupling via electromagnetic radiation, i.e. the transfer of energy without physical contact between two systems including, on the one hand, inductive coupling and, on the other hand, capacitive coupling. The primary antenna is then preferably comprised in the group comprising: a coil, a loop or a wire segment or a combination of these conductive elements.
Here, the term “parallel” is understood to mean that the angle generated by the axial directions of each antenna is smaller than or equal to 30 degrees. In this case, the electromagnetic coupling between the two antennas is optimal, notably improving the communication performance of the passive radiofrequency transponder.
Here, the median plane of the coil and of the helical spring should first be defined. By definition, it is a fictional plane separating the object into two equal portions. In our case, this median plane is perpendicular to the axis of each antenna. Lastly, here the term “central region” is understood to mean that the relative distance between the median planes is smaller than one tenth of the length of the radiating antenna.
Thus, since the electrical current strength is of maximum magnitude at the centre of the radiating antenna, the magnetic field induced by this current is also maximum at the centre of the radiating antenna, and thus it is ensured that the inductive coupling between the two antennas is optimal, thereby improving the communication performance of the passive radiofrequency transponder.
By defining the relative dimensions of the primary antenna with respect to the characteristics of the helical spring of the radiating antenna, it is ensured that the distance between the two antennas will be smaller than the diameter of the primary antenna in the case where the primary antenna is located inside the radiating antenna. Thus, the electromagnetic coupling between the two antennas and therefore the communication performance of the radiofrequency transponder are optimized in transmission and in reception.
Likewise, outside of the region of the radiating antenna that is located plumb with the electronic portion and therefore with the primary antenna, a ratio of the helix pitch to the winding diameter higher than 0.8 for a loop of the radiating antenna has the effect of stretching the helical spring. Thus, the length of wire needed to cover a nominal distance of the radiating antenna is decreased. Thus, the resistance of the radiating antenna is decreased. Therefore, for a given electric field, the strength of the electrical current flowing through the radiating antenna is of higher magnitude at the natural frequency of the antenna, this allowing the communication performance of the radiofrequency transponder to be improved. In addition, stretching the helical spring allows the efficiency of the radiating antenna to be improved by improving the ratio between the radiation resistance and loss resistance thereof, this also allowing the electric field radiated by the radiating antenna for a given flow of electrical current through the radiating antenna to be maximized. Lastly, for the radiating antenna of given pitch, stretching the radiating antenna allows the volume occupied by the helical spring to be decreased. Thus, in a constrained dimensional environment, such as the thickness of a tyre casing, it is possible to increase the thickness of insulating rubber surrounding the radiating antenna in this first region. This electrical insulation minimizes losses and therefore improves the communication performance of the radiofrequency transponder, both in transmission and in reception. Of course, it is ideal for each of the loops of the first region of the radiating antenna to be elongated, this correspondingly improving the communication performance of the passive radiofrequency transponder, in particular when it is an RFID tag.
The term “plumb with two reinforcing elements” is understood to mean that the orthogonal projection of the element, in this case the radiating dipole antenna, onto the plane defined by two parallel reinforcing elements of the main part of the at least one carcass reinforcement layer intersects these two reinforcing elements when the tyre casing is in the green tyre state.
Finally, the fact that the characteristic dimension of the radiating dipole antenna, which dimension is defined by the first longitudinal axis, is situated plumb with several reinforcing elements of the carcass reinforcement layer ensures that the passive radiofrequency transponder is in a controlled position in the thickness of the tyre casing, notably when it is in the green tyre state. Specifically, this configuration reduces the possible shifting of the radiating dipole antenna within the various non-crosslinked layers, notably with respect to the carcass reinforcement layer, when the tyre casing is being built up in the green state. Because the main carcass reinforcement layer of the tyre casing runs from one bead wire to the other, that provides a wide region in which the passive radiofrequency transponder can be installed, and be operational, in the tyre casing. Specifically, the quantity of an elastomeric material surrounding the passive radiofrequency transponder is thus controlled, so that the length of the radiating dipole antenna can be tuned to the electrical environment of the radiating dipole antenna within the tyre reliably and robustly. However, with the carcass reinforcement of the tyre casing comprising a layer of metal reinforcing elements defining a direction of reinforcement, it is appropriate to incline the first longitudinal axis of the radiating dipole antenna by an angle of at least 45 degrees with respect to this direction of reinforcement. Preferentially, this angle is at least 60 degrees and very preferentially the first longitudinal axis of the radiating dipole antenna is perpendicular to the direction of reinforcement. This inclination is necessary in order to limit the radioelectric disturbances of the radiating dipole antenna which are generated by the shielding defined by the metal carcass reinforcement. The perpendicularity of the radiating dipole antenna with respect to the carcass reinforcement minimizes these disturbances. An angle of 45 degrees allows an operation of the radiating dipole antenna which is sufficient for reading the passive radiofrequency transponder at over a metre from a tyre casing mounted on the rim, whilst an angle of 30 degrees doubles the radioelectric disturbances of the radiating dipole antenna.
Finally, the radiofrequency transponder is situated in the bead and sidewall region of the tyre casing, notably between the bead wire and the crown reinforcement of the crown block, so as to facilitate communication between it and an external radiofrequency reader notably in operation on the vehicle. Specifically, because the elements of the bodywork of the vehicle which are generally made of metal, such as the wheel or the wing hinder propagation of radioelectric waves to or from the passive radiofrequency transponder situated with the tyre casing, notably in the UHF frequency range, installing the passive radiofrequency transponder in the sidewall and bead region, radially on the outside of the bead wire, of the tyre casing makes it easier for the passive radiofrequency transponder to be interrogated and read by an external radiofrequency reader from a long distance in numerous positions of the external radiofrequency reader when the tyre casing is in service on a vehicle. The communications with the passive radiofrequency transponder are therefore robust and reliable. Although not essential for radiofrequency communication, the passive radiofrequency transponder is situated on the inside of the tyre casing. It is then incorporated into this casing during the manufacture of the tyre casing, thereby safeguarding the read-only data contained in the memory of the electronic chip of the passive radiofrequency transponder such as, for example, the tyre casing identifier. The alternative is to use techniques known in the prior art to affix a patch made from an elastomer compound containing said passive radiofrequency transponder to the external surfaces of the tyre casing such as, for example, to the layer of inner liner or to the sidewall. This operation may be performed at any moment during the course of the life of the tyre casing, making the tyre casing data contained in the memory of the electronic chip of the passive radiofrequency transponder less reliable.
Optionally, with the radiating dipole antenna comprising a second region in which the radiating dipole antenna is located plumb with the electronic portion, the ratio between the helix pitch P2 and the winding diameter D2 for each loop of the second region is lower than or equal to 0.8.
Specifically, in this second region of the radiating dipole antenna, and more particularly in the region located plumb with the primary antenna, the effect expected from the radiating dipole antenna is electromagnetic, and in particular inductive, coupling with the primary antenna of the electronic portion. Thus, a first lever for improving this coupling is to increase the inductance of the radiating antenna in this second region, this amounting to contracting the helical spring. In addition, contracting the radiating dipole antenna in this second region also promotes the transfer of energy between the primary antenna and the radiating dipole antenna by increasing, for a given length of the primary antenna located facing the radiating dipole antenna, the area of exchange furnished by the radiating dipole antenna. This improvement in energy transfer leads to a better communication performance being obtained from the passive radiofrequency transponder.
Preferably, the ratio between the helix pitch and the winding diameter of each of the loops of the helical spring in the first region of the radiating antenna is lower than 3, and preferably lower than 2.
Although it is advantageous to improve the radioelectric performance of the radiating antenna, it is necessary to also not neglect the other functions that it must perform. In particular, the helical spring is an extendable structure designed to withstand the three-dimensional stresses that the radiofrequency transponder in a tyre casing will have to face from the building of the tyre casing to the use of the tyre casing as an object of mobility on the vehicle. Thus, it is recommended to limit the amount by which the radiating antenna is stretched in this first region in order to ensure the radiating antenna preserves a sufficient suppleness on the whole and thus to ensure the physical integrity of the passive radiofrequency transponder.
Preferably, the primary antenna being connected to the terminals of a circuit board comprising the electronic chip, the electrical impedance of the primary antenna is matched to the electrical impedance of the circuit board of the radiofrequency transponder.
The term “electrical impedance of the circuit board” is understood to mean the electrical impedance across the terminals of the primary antenna, this representing the electrical impedance of the circuit board comprising at least one electronic chip and a printed circuit board to which the electronic chip is connected.
By matching the impedance of the primary antenna to that of the circuit board, the radiofrequency transponder is optimized at the communication frequency by improving the gain and achieving a circuit board of more selective form factor and narrower passband. Thus, the communication performance of the radiofrequency transponder is improved for a given amount of energy transmitted to the radiofrequency transponder. This in particular results in an increase in the read distance of the radiofrequency transponder for a given emitted radioelectric power. The impedance match of the primary antenna is obtained by adjusting at least one of the geometric features of the primary antenna, such as, for example, the diameter of the wire, the material of this wire and the length of the wire.
The impedance match of the primary antenna may also be obtained by adding an impedance-matching circuit made up of additional electronic components between the primary antenna and the electronic circuit, such as, for example, filters based on an inductor, capacitors and transmission lines.
The impedance match of the primary antenna may also be obtained by combining features of the primary antenna and features of an impedance-matching circuit.
According to one particular embodiment, the electronic chip and at least one portion of the primary antenna are embedded in a stiff and electrically insulating mass, such as, for example, high-temperature epoxy resin. This assembly forms the electronic portion of the radiofrequency transponder.
Thus, the electronic portion comprising at least one portion of the primary antenna and the electronic chip connected to the printed circuit board is stiffened, making the mechanical connections between the components thereof more reliable with respect to the thermomechanical stresses to which the tyre casing is subjected, both while it is being connected and while it is in use.
This also allows the electronic portion of the radiofrequency transponder to be manufactured independently of the radiating antenna or of the tyre casing. In particular, for example, using a micro-coil of a number of turns as primary antenna allows miniaturization of the electronic component comprising the primary antenna and the electronic chip to be envisaged.
According to another embodiment, the portion of the primary antenna not embedded in the stiff mass is coated with an electrically insulating material.
Thus, if the primary antenna is not entirely contained in the stiff and electrically insulating mass of the electronic portion, it is useful to insulate it via a coating made of an electrically insulating material, such as those employed for an insulating sheath of an electrical cable.
According to one specific embodiment, the tyre casing comprises a fourth layer of elastomer compound situated axially on the outside of the main part of at least one carcass reinforcement layer with respect to the reference axis and axially on the inside of the second and/or third layer of elastomer compound with respect to the reference axis.
Thus, this configuration of tyre casing provides a compromise in the performance of the bead and of the sidewall that are differentiating and the passive radiofrequency transponder can be inserted in contact with this fourth layer of elastomer compound.
According to another specific embodiment, with the tyre casing comprising an airtight layer of elastomer material, which is to say a layer that is highly impermeable to air, this layer being situated furthest towards the inside of the tyre casing with respect to the reference axis, the tyre casing comprises a fifth layer of elastomer compound situated on the inside of the main part of the at least one carcass reinforcement layer with respect to the reference axis.
This configuration of tyre casing makes it possible, for example, to improve the service life of the carcass of the tyre casing. Specifically, the fifth layer of elastomer compound comprises constituents which make it possible in particular to fix the oxygen in the air, thereby limiting the oxidation of the other products of the tyre casing which are situated axially on the outside of this fifth layer of elastomer compound.
The passive radiofrequency transponder may therefore be in contact with this fifth layer of elastomer compound.
According to one particular embodiment, the tyre casing comprises a reinforcement layer formed of reinforcing elements inserted between two layers of rubber.
These are special-purpose casings which, depending on the type of use or in-service stress loadings, require localized reinforcements in the bead for example in order to prevent rubbing between the wheel and the tyre casing. This reinforcement reinforcing layer may also be located in a certain region, particularly the axial ends of the crown block, to constrain the geometry of the crown block and of the tyre casing under severe thermomechanical stress loadings This reinforcement reinforcing layer generally has at least one free end. The passive radiofrequency transponder may then be in contact with or close to the free end of this reinforcement reinforcing layer made of elastomer compound.
According to one specific embodiment, the passive radiofrequency transponder is partially encapsulated in a mass of electrically insulating elastomer compound.
The term “electrically insulating” is understood here to mean that the electrical conductivity of the elastomer compound is at least below the conductive charge percolation threshold of the compound.
According to a final specific embodiment, the relative dielectric constant of the encapsulating mass is lower than 10.
This value of relative dielectric permittivity of the elastomer compounds that make up the encapsulating mass ensures the stability of the environment in which the passive radiofrequency transponder is situated, thus making the subject matter of the invention robust. Thus, the encapsulating mass assures the radioelectric waves of an environment that remains constant, thus robustly fixing the dimension of the radiating dipole antenna for operation at the target communication frequency.
According to another specific embodiment, the tensile elastic modulus of the encapsulating mass is lower than the tensile elastic modulus of at least one elastomer compound adjacent to said encapsulating mass.
This then forms an assembly that makes the passive radiofrequency transponder easier to fit into the green tyre casing while restricting the mechanical singularity that the passive radiofrequency transponder constitutes within the tyre casing. A conventional bonding-rubber layer will possibly be employed, if necessary, to secure this assembly to the tyre casing.
In addition, the stiffness and electrical-conductivity characteristics of the elastomer compound ensure a quality mechanical insertion and electrical insulation of the passive radiofrequency transponder within the tyre casing. Thus, the operation of the radiofrequency transponder is not perturbed by the tyre casing.
According to a first preferred embodiment, the passive radiofrequency transponder is situated at an interface defined by a surface of a layer of elastomer compound of the tyre casing.
This is an embodiment which makes the passive radiofrequency transponder easier to fit into the architecture of the tyre casing. The fitting of the passive radiofrequency transponder takes place directly in the means for building the green tyre by said passive radiofrequency transponder being placed onto the external surface of a layer of elastomer compound. This layer of elastomer compound may also be a skim layer. The passive radiofrequency transponder will then be covered with a second layer of elastomer compound. In this way, the passive radiofrequency transponder is therefore fully encapsulated by the components of the tyre casing. It is therefore embedded within the tyre casing, ensuring that it cannot be falsified when the memory of the electronic chip is write protected.
As a preference, with the interface being defined by another layer of elastomer compound or a reinforcement layer, the passive radiofrequency transponder is situated at a distance of at least 5 millimetres from the ends of the layers that make up the interface, preferentially of at least 10 millimetres from the end of a metal reinforcement layer.
The passive radiofrequency transponder presents as a foreign body in the build of the tyre, constituting a mechanical singularity. The ends of the layers at the interface also constitute mechanical singularities. To safeguard the endurance of the tyre casing, it is preferable for the two singularities to be distanced from one another by a certain distance. The greater this distance, the better, the minimum distance of the influence of a singularity being of course proportional to the size of this singularity. The singularity formed by the end of a layer becomes more sensitive the greater the stiffness of the layer in comparison with the stiffness of the adjacent layers such as, for example, a reinforcement reinforcing layer or a carcass reinforcement layer. When the reinforcers are metallic in nature or made of a textile that has just as high a stiffness, such as in the case of aramid, for example, it is appropriate to keep the two singularities at least 10 millimetres apart.
According to a second preferred embodiment, the passive radiofrequency transponder is situated on the inside of a layer of elastomer compound of the tyre casing.
This second embodiment has the advantage of leaving the choice as to the exact position of the passive radiofrequency transponder depending on the thickness of the tyre casing, unlike in the first preferred embodiment which imposes the position by the interface between the layers of elastomer compound. It is thus also possible to encapsulate the passive radiofrequency transponder in a mass of elastomer compound that is uniform from an electrical insulation and stiffness viewpoint, facilitating good radiofrequency and mechanical operation of the passive radiofrequency transponder. This also allows the radiofrequency transponder to be prepared for incorporation into the layer of elastomer compound away from the means used for building the tyre casing, and this proves to be more productive. Thus, this second preferred embodiment offers a wider choice for the installation of the passive radiofrequency transponder within the tyre casing.
Advantageously, the first longitudinal axis of the radiating dipole antenna of the passive radiofrequency transponder is perpendicular to the thickness of the layer of elastomer compound.
The layers of elastomer compound are generally thick layers partially superposed on one another to build a tyre casing. In order to gain best control over the positioning of the passive radiofrequency transponder within the tyre casing it is preferable for the main dimension of the passive radiofrequency transponder, namely the first longitudinal axis, to be oriented perpendicular to the thickness of the layer of elastomer compound. This avoids the risk of the radiofrequency transponder, inclined with respect to the surface of the elastomer compound, passing through the external surface of the layer of elastomer compound during manufacture of the tyre and into another layer. Such an instance could potentially be harmful to the endurance of the tyre casing.
Highly advantageously, the passive radiofrequency transponder is situated at a distance of at least 0.3 millimetres from the surfaces of the layer of elastomer compound.
A “distance of at least 0.3 millimetres” is understood to mean that any external material point of the first object, in this instance the passive radiofrequency transponder potentially equipped with its encapsulating mass, is situated at a distance that is greater than or equal to 0.3 millimetres from any material point of the second object, in this instance the surfaces of the layer of elastomer compound. In particular, this distance of 0.3 millimetres is to be measured in the cured state.
This then prevents the risk of any potential shifting of the passive radiofrequency transponder within the layer of elastomer compound under thermomechanical stresses, or any spread in the positioning of the passive radiofrequency transponder within the layer of elastomer compound during the phase of manufacturing the tyre casing. This positioning will not cause the passive radiofrequency transponder to leave the layer of elastomer compound. This then ensures controlled mechanical and electrical insulation of the passive radiofrequency transponder within the layer of elastomer compound, which in turn ensures the endurance of the tyre casing and of the radiofrequency transponder while at the same time guaranteeing good radiofrequency operation.
According to one specific embodiment, the radioelectric communication with the radiofrequency reader occurs in the UHF band and most specifically in the range comprised between 860 and 960 MHz.
Specifically, in this frequency band, the length of the radiating antenna is inversely proportional to the communication frequency. Furthermore, outside of this frequency band, radioelectric communication is highly perturbed or even impossible through standard elastomeric materials. Thus, this is the best compromise between the size of the radiofrequency transponder and its radioelectric communication, in particular in the far-field, making it possible to have communication distances that are satisfactory for the field of tyres.
According to another particular embodiment, the length L0 of the radiating antenna is comprised between 30 and 50 millimetres.
Specifically, in the frequency range between 860 and 960 MHz and depending on the relative dielectric permittivities of the elastomer compounds surrounding the radiofrequency transponder, the total length of the helical spring, which is tailored to the half-wavelength of the radioelectric waves transmitted or received by the radiofrequency transponder, is located in the interval between 30 and 50 millimetres, and preferably between 35 and 45 millimetres. In order to optimize the operation of the radiating antenna at these wavelengths, it is recommended to perfectly tailor the length of the radiating antenna to the wavelength.
Advantageously, the winding diameter of the helical spring in the first region of the radiating antenna is comprised between 0.6 and 2.0 millimetres, and preferably between 0.6 and 1.6 millimetres.
This allows the volume occupied by the radiating antenna to be limited and therefore the thickness of electrically insulating elastomer compound around the radiofrequency transponder to be increased. Of course, this diameter of the helical spring in the first region of the radiating antenna may be constant, variable, continually variable or piecewise variable. It is preferable from a point of view of the mechanical integrity of the radiating antenna for the diameter to be constant or continuously variable.
According to one preferred embodiment, the helix pitch of at least one loop of the radiating antenna in the first region of the radiating antenna is comprised between 1 and 4 millimetres, and preferably between 1.3 and 2 millimetres.
This makes it possible to ensure that the ratio of the helix pitch to the winding diameter of the spring, or at least one loop, in the first region of the radiating antenna is lower than 3, guaranteeing a minimum of elongation of the helical spring. In addition, this pitch may also be constant or variable throughout the first region of the radiating antenna. Of course, it is preferable for the pitch to be continuously variable or variable with small transitions in variation in order to avoid singular points in the radiating antenna that would form mechanical weaknesses in the radiating antenna.
According to one advantageous embodiment, the diameter of the wire of the radiating antenna is comprised between 0.05 and 0.25 millimetres, and ideally between 0.12 and 0.23 millimetres.
In this wire range, loss resistance is certain to be low, thus improving the radioelectric performance of the radiating antenna. In addition, limiting the diameter of the wire allows the distance between the radiating antenna and the electrical conductors to be increased by increasing the thickness of the electrically insulating elastomer compounds. However, it is necessary for the wire to preserve a certain mechanical strength in order to be able to bear the thermomechanical stresses that it will undergo in a highly stressed environment such as a tyre casing, without optimizing the breaking stress of the material of these wires, which is generally mild steel. This makes it possible to ensure the radiating antenna represents a satisfactory technical/economical compromise.
Advantageously, the first pitch P1 of the radiating dipole antenna, which corresponds to the helix pitch of the radiating dipole antenna in the first region is greater than the second pitch P2 of the radiating dipole antenna which corresponds to the helix pitch of the radiating dipole antenna in the second region in which the radiating dipole antenna is situated plumb with the electronic portion.
By requiring that the helix pitch P2 of the radiating dipole antenna in a second region in which the radiating dipole antenna is located plumb with the electronic portion be smaller than the pitch P1 of the radiating dipole antenna outside this region, the electromagnetic aptitudes of the radiating dipole antenna in this region are favoured to the detriment of its radiating efficacy, which are promoted in the first region of the radiating dipole antenna. Thus, the compression of the helix pitch of the radiating dipole antenna improves the inductance of the antenna in this region. For a given flow of electrical current through the radiating dipole antenna, this is a lever arm that is essential to increase the magnetic field generated by the antenna. Furthermore, this improvement in the inductance of the radiating dipole antenna is obtained without necessarily modifying the winding diameter of the radiating antenna. In addition, for a primary antenna of given length, the compression of the pitch of the radiating dipole antenna plumb with the primary antenna of the electronic portion ensures a larger area of exchange between the two antennas, thus also improving the electromagnetic coupling between the two antennas. Thus, the communication performance of the radiofrequency transponder is thereby improved. Lastly, the compression of the pitch of the radiating dipole antenna allows the manufacturing tolerances on the radiating dipole antenna to be minimized and better controlled in this second region, in particular as regards the definition of the winding diameter of the radiating dipole antenna. Thus, the scrap rate for the radiating dipole antennas is reduced since it is the control over this diameter that governs the positioning of the electronic portion with respect to the radiating dipole antenna.
Highly advantageously, with the electronic portion being placed inside the radiating antenna, the first inside diameter D1′ of the radiating dipole antenna in the first region is smaller than the second inside diameter D2′ of the radiating dipole antenna in a second region, and the electronic portion is circumscribed by a cylinder of which the axis of revolution is parallel to the first longitudinal axis and of which the diameter is larger than or equal to the first inside diameter D1′ of the radiating dipole antenna.
By ensuring that the cylinder that circumscribes the electronic portion has an axis of revolution parallel to the first longitudinal axis and a diameter larger than or equal to the first inside diameter of the radiating dipole antenna, the first region of the radiating antenna therefore forms a stop with respect to the axial movement of the electronic portion. The fact that this first region is situated on each side of that region of the radiating dipole antenna that is situated plumb with the electronic portion because of the centred positioning of the electronic portion with respect to the radiating dipole antenna, ensures that there are therefore two mechanical end stops situated axially on the outside of the electronic portion and limiting any axial movement of the electronic portion of the radiofrequency transponder. In addition, because the diameter of the cylinder circumscribing the electronic portion is situated on the inside of the radiating antenna in the second region, this diameter has to be smaller than the second inside diameter of the radiating antenna. Thus, any radial shifting of the electronic portion is confined by the second inside diameter of the radiating dipole antenna. In conclusion, the movement of the electronic portion is limited, this allowing the communication performance of the radiofrequency transponder to be ensured while ensuring a physical integrity of the electronic portion and of the radiating dipole antenna of the passive radiofrequency transponder. Lastly, the endurance of the tyre casing accommodating this radiofrequency transponder is also not impacted by this choice of design. Furthermore, the radiofrequency transponders are made easier to handle for fitting into the structure of the tyre casing without the need to take additional precautions.
The invention will be better understood by means of the following detailed description. These applications are given solely by way of example and with reference to the appended figures, throughout which the same reference numerals denote identical parts, and in which:
Below, the terms “tyre” and “pneumatic tyre” are employed equivalently and refer to any type of pneumatic or non-pneumatic tyre.
Of course, instead of solely modifying the helix pitch or the winding diameter of each loop, it is possible to modify both parameters simultaneously. Only the ratio obtained via these two modifications will have an impact on the communication performance of the radiating antenna.
Specifically, the resistance of a conductive wire is proportional to the curvilinear length of the wire. The higher the ratio of the helix pitch to the winding diameter of the loop, the shorter the curvilinear length of the wire. Thus, the lower the electrical resistance of the loop. In conclusion, the radioelectric properties of the loops of the radiating antenna are improved by minimizing this electrical resistance. By minimizing the electrical resistance of the radiating antenna in the first region of the radiating antenna, the radiation efficiency of the antenna is improved both in transmission and in reception, the antenna mainly consisting of this first region. In addition, minimizing the electrical resistance of the antenna ensures a maximum electrical current is generated for a given electrical potential difference. Thus, the radioelectric performance and therefore the communication performance of the radiofrequency transponder are thereby improved.
As regards the second region of the radiating antenna, the radiation efficiency of this second region, which is smaller than the first region, is not essential. Specifically, the main function of this second region is to ensure electromagnetic coupling to the primary antenna of the electronic portion. This electromagnetic coupling is mainly due to inductive coupling if the primary antenna is a coil of a number of turns. For this coupling to occur, the radiating antenna must first generate a magnetic field. This magnetic field is in particular dependent on the inductance of the radiating antenna. To maximize the inductance of a coil, it is recommended to decrease the ratio of the helix pitch to the winding diameter of the coil or to increase the number of loops of the coil. By decreasing the ratio of the helix pitch to the winding diameter of the loops of the second region of the radiating antenna, the inductive coupling is maximized by increasing the inductance of the antenna. In addition, if this ratio is decreased by modifying only the helix pitch of the antenna, the number of turns making up the second region of the antenna is increased, this increasing the area of energy transfer between the two antennas. This increase in the area of energy transfer is of course favourable to the communication performance of the radiofrequency transponder.
In addition, the radiofrequency transponder will be positioned axially on the outside with respect to the axially inner end of the bead. This is region that is mechanically stable as it does not experience sizeable unforeseen variations in thermomechanical deformation. Finally, the passive radiofrequency transponder 1 will be placed radially between the radially upper end of the bead wire and the axial end of the crown block of the tyre casing. This positioning in the radial direction makes it easier for the passive radiofrequency transponder incorporated into a tyre casing of a land vehicle to communicate with a radiofrequency reader situated outside the land vehicle as there are few conducting elements interposed between the radiofrequency reader and the passive radiofrequency transponder 1.
The radiofrequency transponder 1 here comprises a radiating antenna 10 and an electronic portion located inside the radiating antenna 10. The electronic portion comprises an electronic chip connected to a printed circuit board and a primary antenna consisting of a conducting wire comprising seventeen rectangular turns connected to the printed circuit board. The face of the printed circuit board opposite to the primary antenna comprises a galvanic circuit of meander shape forming a line of 10 millimetres length and of 1 millimetre width. Lastly, the diameter of the cylinder circumscribing the primary antenna is 0.8 millimetres.
The circuit board thus formed is embedded in a mass 30 of epoxy resin, ensuring the mechanical reliability of the electronic components and the electrical insulation of the circuit board. The cylinder circumscribing the stiff mass 30 has a diameter of 1.15 millimetres and a length of 6 millimetres.
The length L0 of the radiating antenna 10 is here 45 millimetres and corresponds to one half-wavelength of radioelectric waves at a frequency of 915 MHz in a medium of relative dielectric permittivity of about equal to 5. The radiating antenna 10 is produced using a steel wire 12 of 0.225 millimetre diameter the surface of which is coated with a layer of brass.
The radiating antenna 10 may be divided into two main regions. The first region 101 corresponds to the section of the radiating antenna that is not located plumb with the electronic portion. It comprises two sub-regions 101a and 101b flanking on either side the stiff and insulating mass 30.
Each sub-region 101a, 101b has a length L1 of 19 millimetres and comprises 12 circular turns of a constant winding diameter D1 of 1.275 millimetres. This defines inside and outside diameters of 1.05 and 1.5 millimetres, respectively. The helix pitch P1 of the circular turns is of 1.55 millimetres. Thus, the ratio of the helix pitch P1 to the winding diameter D1 of the turns is 1.21. The axially outer ends of each sub-region 101a and 101b ends in 2 adjoined turns. Thus, the high ratio ensures the efficacy of the radioelectric properties of the radiating antenna 10 is maximized in this region 101. In addition, the contact between the turns located outermost on the radiating antenna 10 prevents the helical springs from becoming interlaced with one another during handling of the radiofrequency transponders. As most of the turns of the first region 101 of the radiating antenna 10 have a ratio higher than 0.8, the radioelectric performance of the radiofrequency transponder 1 is clearly improved.
In the second region 102 of the radiating antenna 10, which corresponds to the section of the radiating antenna 10 located plumb with the electronic portion, the radiating antenna has a length of 7 millimetres. The helical spring has a constant helix pitch P2 of 1 millimetre and a constant winding diameter D2 of 1.575 millimetres. Thus, the inside diameter of the helical spring of the second region of the radiating antenna is 1.35 millimetres. This makes it possible to have a ratio of the helix pitch to the winding diameter that is constant of the order of 0.63. This ratio allows the inductance of the second region 102 of the radiating antenna 10 to be maximized with respect to the first region 101, this allowing the efficacy of the electromagnetic coupling to the electronic portion to be improved.
In this particular case, in the first region 101 the inside diameter of the radiating antenna 10, which is equal to 1.05 millimetres, is smaller than the diameter, equal to 1.15 millimetres, of the mass 30 as represented by the cylinder circumscribing the electronic portion. Thus, the sub-regions 101a and 101b of the first region 101 of the radiating antenna 10 form mechanical stops that limit the axial movement of the mass 30 inside the radiating antenna 10. The electronic portion is installed by inserting the stiff and insulating mass 30 into the radiating antenna 10.
In addition, the diameter of the cylinder circumscribing the primary antenna is much larger than one third of the inside diameter of the helical spring of the second region 102 of the radiating antenna. Although the cylinder circumscribing the primary antenna is not coaxial with the axis of revolution U of the radiating antenna 10, it is substantially parallel thereto. Furthermore, the minimum distance between the second region 102 of the radiating antenna 10 and the primary antenna is smaller than 0.3 millimetres, i.e. much smaller than one quarter of the inside diameter of the radiating antenna 10. This proximity of the antennas is permitted by the compressed pitch P2 applied in the second region 102 of the radiating antenna 10, which allows a lower tolerance to be obtained for the dimensions of the spring and in particular for the winding diameter D2. In addition, this proximity ensures better quality electromagnetic coupling between the two antennas. Of course, this electromagnetic coupling could have been improved by using turns of identical shape in the primary antenna and in the radiating antenna, such as circular turns for example. This coupling could also have been optimized by making the axes of the two antennas coaxial, this amounting to placing the circuit board inside the primary antenna in such a way as to minimize the axial dimension of the electronic portion. Thus, the quality of the area of transfer of electromagnetic energy between the two antennas would have been optimal.
Other specific embodiments, in particular in the case of variation of the winding diameter of the helical spring between the first and second regions of the radiating antenna, particularly in instances in which the inside diameter of the first region of the radiating antenna is smaller than the diameter of the cylinder circumscribing the electronic portion, may be employed.
In the case where the ratio between the helix pitch and the winding diameter of the loop of the first region 101 of the radiating antenna 10 is increased by decreasing the winding diameter of the steel wire, the volume occupied by the radiofrequency transponder 1 within the mass 3 of elastomeric material is decreased.
This allows, in a first application, the thickness of each of the blocks 3a and 3b of the identification tag 2 to be decreased while keeping the same distance between the external surface of the identification tag 2 and the first region 101 of the radiating antenna 10. This decrease in the thickness of the identification tag 2 will facilitate its introduction into an object to be identified, while preserving the same electrical-insulation potential. In a second application, this allows the distance between the first region 101 of the radiating antenna 10 and the external surface of the identification tag 2 to be increased. This second application allows radioelectric performance to be improved and therefore the communication performance of the radiofrequency transponder 1 placed in the identification tag 2. Specifically, the electrical insulation of the tag 2 is proportional to the distance between the first region 101 of the radiating antenna 10 and the external surface of the tag 2. The radioelectric operation of the radiofrequency transponder 1 is improved, or stays the same if this distance has reached its efficacy asymptote, by a better electrical insulation of the identification tag 2.
The circumferential direction of the tyre, or longitudinal direction, is the direction that corresponds to the periphery of the tyre and is defined by the direction of running of the tyre casing.
The transverse or axial direction of the tyre is parallel to the axis of rotation, or reference axis, of the tyre casing.
The radial direction is a direction which crosses the reference axis of the tyre casing and is perpendicular thereto.
The axis of rotation of the tyre casing is the axis about which it turns in normal use.
A radial or meridian plane is a plane that contains the axis of rotation of the tyre.
The circumferential median plane, or equatorial plane, is a plane that is perpendicular to the reference axis of the tyre casing and divides the latter into two halves.
The bead 84 consists of the bead wire 85, around which the main part of the carcass reinforcement layer 87 is wound, with a turn-up 88 situated in the outer region of the tyre casing 100. The turn-up 88 of the carcass layer ends with a free edge 881. A first layer of rubber compound 91, called bead wire filler, is situated radially externally and adjacent to the bead wire 85. It has a radially outer free edge 911 bearing on a face of the main part of the carcass reinforcement layer 87 (more precisely on the outer skim of the carcass reinforcement layer 87, without direct contact between the cords of the carcass layer and the electronic unit). A fourth layer of rubber compound 92, called “reinforcing filler”, is adjacent thereto. It has two free edges. The first free edge 921 is situated radially internally and bears on the turn-up 88 of the carcass reinforcement layer. The other free edge 922 is situated radially externally and ends on the face of the main part of the carcass reinforcement layer 87. Finally, the sidewall 83 is defined by means of a third layer of elastomer compound 94 covering both the fourth layer of elastomer compound 92 and the main part of the carcass reinforcement layer 87. The sidewall defined by the external surface of the third layer of elastomer compound 94 which has a free edge 941 situated radially on the inside ends in the turn-up 88 of the carcass reinforcement layer.
The airtight inner liner 90, which is adjacent to the main part of the carcass reinforcement layer 87 in this configuration, is located on the inner region of the tyre casing 100. It ends with a free edge 901 adjacent to the main part of the carcass layer 87. Finally, a second layer of elastomer compound 93, referred to as a bead protector, protects the carcass layer and the radially interior ends 901, 921 and 941 of the airtight inner liner 90, of the fourth layer of elastomer compound 92 and of the third layer of elastomer compound 94 respectively. The outer face of this second layer of elastomer compound 93 is able to be in direct contact with the rim flange during mounting of the tyre casing 100 on the wheel. This second layer of elastomer compound 93 has three radially outer free edges. The first free edge 931 is situated in the inner region of the tyre casing 100. The second free edge 932 is situated in the outer region of the tyre casing 100. Finally, the third free edge 933 constitutes the interior end 841 of the bead 84.
A bead 84 and its connected sidewall 83 of this tyre casing 100 is equipped with passive radiofrequency transponders, numbered 1, possibly with suffixes, which are situated in the exterior region of the tyre casing 100. The first passive radiofrequency transponder 1, having been encapsulated beforehand in an electrically insulating encapsulating rubber, is positioned on the outer face of the first layer of the bead wire filler 91. It is positioned at a distance of 20 millimetres from the free edge 881 of the turn-up 88 of the carcass layer that constitutes a mechanical singularity, that is to say beyond 10 millimetres away. This position ensures a region of mechanical stability for the radiofrequency transponder 1 that is beneficial to the mechanical endurance thereof In addition, embedding it within the very structure of the tyre casing 100 gives it good protection against mechanical attacks coming from outside the tyre casing 100. Finally, the first longitudinal axis of the passive radiofrequency transponder is in this case positioned circumferentially, which ensures an inclination perpendicular to the metal reinforcers of the main part 87 of the carcass reinforcement layer, favouring the radioelectric performance of the radiating dipole antenna and the positioning of the passive radiofrequency transponder within the structure of the tyre casing during manufacture of the tyre casing (tyre building and curing steps). Of course, this tyre 100 may be reinforced by a reinforcement layer, not depicted, situated, for example, between the fourth layer of elastomer compound 92 and the second 93 and/or third 94 layer(s) of elastomer compound. This reinforcement layer is generally made up of reinforcing elements which are oriented radially and, for example, sandwiched between two skim layers. This reinforcement layer has a radially outer end situated radially outside the end 881 of the turn-up 88 of the carcass reinforcement layer. The radiofrequency transponder 1 is spaced apart from the radially outer end of the reinforcement layer by at least 5 millimetres or even 10 millimetres if the reinforcing elements are metallic in nature.
In general, it is preferable for the passive radiofrequency transponder to be positioned at a radial distance of between 20 and 40 millimetres from the radially outer end of the bead wire 85 in order to be in a region of the tyre casing 100 that is mechanically stable during operation, as this guarantees the physical integrity of the radiofrequency transponder. In addition, this positioning is ensured to be radially on the outside of the rim flange, allowing good radiocommunication performance by limiting the disturbances associated with the, often metallic, nature of the wheel.
The second radiofrequency transponder 1bis, having optionally been encapsulated in an electrically insulating encapsulating rubber compatible with or similar to the material of the third layer of elastomer compound 94, is positioned on the inside of the third layer of elastomer compound 94. The material similarity between the third layer of elastomer compound 94 and the encapsulating rubber ensures that the radiofrequency transponder ibis is easily installed inside the sidewall 83 during the process of manufacturing the tyre casing. The radiofrequency transponder 1bis is simply placed within the material via a slit in the raw exterior face of the third layer of elastomer compound 94 during the building of the tyre casing 100 such that the first longitudinal axis of the radiating dipole antenna forms an angle of at least 45 degrees with respect to the radial direction of the tyre casing, this corresponding to the direction of reinforcement of the carcass reinforcement. Building the green tyre body and pressurizing it in the curing mould ensure that the radiofrequency transponder 1bis is, in the cured state, positioned as shown. This radiofrequency transponder 1bis is situated far from any free edge of any other constituent of the tyre casing 100 practically at the equator of the sidewall 83 providing the greatest radiofrequency communication distance. In particular, it is spaced from the free edge 932 of the bead protector, from the free edge 881 of the carcass reinforcement layer turn-up 88 and from the free edges 911 and 922 of the filler rubbers. Its positioning ensures improved communication performance with an external radiofrequency reader. Cyclic stress loadings during running will not be disruptive due to the mechanical decoupling between the radiating antenna and the electronic portion of the passive radiofrequency transponder 1bis. Of necessity, these two transponders are situated axially on the outside of the end 933 of the second layer of rubber compound 93 and therefore of the inner end of the bead 84. They are positioned radially between the radially outer end 851 of the bead wire 85 with respect to the reference axis of the tyre casing 100, and the axial ends 861 of the crown reinforcement 86.
The tyre casing 100 comprises, in particular at the inner region, an airtight inner liner 90 and a layer of elastomer compound 96 interposed between the main part of the carcass layer 87 and the airtight inner liner 90. This component 96 has a radially interior free edge 961 located radially on the inside of the bead wire 85. This layer of elastomer compound 96 extends from one bead 84 to the other bead 84 of the tyre casing 100.
The location of the radiofrequency transponder at the interface between the airtight inner liner 90 and the layer of elastomer compound 96 allows the passive radiofrequency transponder 1 to be mechanically stabilized. It is approximately 40 millimetres radially on the outside of the free edge 931 of the bead protector 93, which means it can be situated radially on the outside of the rim flange when the tyre casing is in operation, mounted on a wheel. By contrast, in order to ensure improved radiocommunication performance, it is preferable to use an encapsulating rubber that is electrically insulating for encapsulating the radiofrequency transponder 1 and to orient the first longitudinal axis of the radiating dipole antenna of the radiofrequency transponder such that the inclination is at least 45 degrees, preferentially at least 60 degrees, with respect to the direction of the metal reinforcers of the carcass reinforcement layer. From the mechanical endurance point of view, this location is ideal for the passive radiofrequency transponder 1, which is protected from any external mechanical attack and from any internal thermomechanical attack. It ideally has a circumferential orientation given that it rests on at least two reinforcing elements of the carcass reinforcement layer 87. This ensures the radiofrequency transponder 1 has an axial position, with respect to the thickness of the tyre casing 100, that allows robust tuning of the resonance of the radiating dipole antenna of the passive radiofrequency transponder 1 when this transponder is incorporated in the tyre casing 100.
The second location of the radiofrequency transponder 1ter according to the invention allows improved radiocommunication performance by being radially further outwards in the tyre casing 100. However, it is advisable for it to be encapsulated in an electrically insulating rubber and for the first longitudinal axis of the radiating antenna to be positioned in such a way that the radiofrequency transponder 1ter is circumferential although an inclination of 45 degrees makes it possible to achieve the desired communication function. Here, in this example, the first longitudinal axis is placed circumferentially. It is preferable for the passive radiofrequency transponder 1ter to be positioned at the interface defined by at least two components of the tyre casing 100 during manufacture thereof. That means that the data contained in the electronic chip of the passive radiofrequency transponder cannot be falsified when this chip has been write-protected after the first writing to the memory associated with the electronic chip.
Again, there is part of the metal carcass reinforcement layer wrapped around a bead wire 85 to form a main part 87 and a turn-up 88 with a end 881.
The turn-up 88 of the carcass reinforcement layer is separated from the main part 87 of the carcass reinforcement layer by a first layer of elastomer compound 91, having a radially outer end 911.
The first layer of elastomer compound 91 is profiled so as to come to rest against the bead wire 85 and provide coupling and uncoupling between the turn-up 88 of the carcass reinforcement layer and the main part 87 of the carcass reinforcement layer.
The turn-up 88 and the main part 87 of the carcass reinforcement layer are said to be coupled if the reinforcing elements of each component are separated by a thickness of elastomer compound that is substantially constant and at most 5 millimetres over a length greater than 15% of the distance between the end 881 of the turn-up 88 of the carcass reinforcement layer and the radially outermost point B of the circle T circumscribing the bead wire 85. In addition, the turn-up 88 and the main part 87 of the carcass reinforcement layer are said to be uncoupled if, radially on the outside of the coupling zone, the thickness of the elastomer compound separating the respective reinforcing elements of the main part 87 and of the turn-up 88 of the carcass reinforcement layer is greater than that of the coupled region.
Depicted axially on the outside of the turn-up 88 of the carcass reinforcement layer is a fourth layer of elastomer compound 92 of which the radially outer end 922 is radially on the inside of the end 881 of the turn-up 88 of the carcass reinforcement layer. According to another embodiment which has not been depicted, the radially outer end 921 of the fourth layer of elastomer compound 92 is radially on the outside of the end 881 of the turn-up 88 of the carcass reinforcement layer.
The radially inner end 921 of the fourth layer of elastomer compound 92 is radially comprised between the points A and B, which are respectively the radially innermost and the radially outermost points of the circle T circumscribing the bead wire 85.
In contact with the fourth layer of elastomer compound 92 and radially below the bead wire 85, there is a second layer of elastomer compound 93 of which the axially outermost end 932 is radially on the inside of the end 922 of the fourth layer of elastomer compound 92. Finally, the radially and axially inner end 933 of the second layer of elastomer compound 93 constitutes the inner end 841 of the bead 84.
Axially in contact with the first layer of elastomer compound 91, with the fourth layer of elastomer compound 92, and with the second layer of elastomer compound 93, there is a third layer of elastomer compound 94. The radially inner end 941 of the third layer of elastomer compound 94 is radially on the inside of the end 922 of the fourth layer of elastomer compound 92.
The bead 84 also comprises a passive radiofrequency transponder 1bis positioned axially on the outside relative to the interface between the turn-up 88 of the carcass reinforcement and the fourth layer of elastomer compound 92. This passive radiofrequency transponder 1bis is placed radially in the region of coupling between the main part 87 of the carcass reinforcement layer and the turn-up 88 of this carcass reinforcement layer, namely between the two points C and D of
This position affords the passive radiofrequency transponder 1bis good mechanical protection and the applicant has discovered experimentally that a distance greater than 2 mm from the metal reinforcing elements of the turn-up 88 of the carcass reinforcement layer provides good robustness of communication with an external reader even if the reading distances are practically identical or very similar compared with a passive radiofrequency transponder positioned at the interface between the turn-up 88 and the fourth layer of elastomer compound 92. The reading distance is thus less susceptible to the unpredictabilities of industrial scale manufacture than when the passive radiofrequency transponder is placed directly at the interface between the fourth layer of elastomer compound 92 and the skim coating of the layer of metal reinforcers of the turn-up 88.
The tyre casing comprises, in the region of the bead 84, a first passive radiofrequency transponder 1 positioned at the interface between the turn-up 88 of the carcass reinforcement layer and the fourth layer of elastomer compound 92. Preferentially, the passive radiofrequency transponder 1 is embedded in an electrically insulating encapsulating mass having a relative dielectric permittivity of less than 10 and of which the extension modulus is lower than the extension modulus of the fourth layer of elastomer compound 92. It is laid out in such a way that the first longitudinal axis of the radiating dipole antenna forms an angle of at least 45 degrees between this first longitudinal axis and the direction of reinforcement of the main part 87 and of the turn-up 88 of the carcass reinforcement layer.
The radiofrequency transponder placed in the region of coupling between the main part 87 and the turn-up 88 of the carcass reinforcement layer, namely between the points C and D, preferentially in the central region. This position is easily delimited by the profiled shape of the first layer of elastomer compound 91 against which the turn-up 88 of the carcass reinforcement layer rests.
A second passive radiofrequency transponder 1′ is placed in the region of the bead 84 at the interface between the second layer of elastomer compound 93 and the fourth layer of elastomer compound 92. Optionally, this radiofrequency transponder 1′ will be placed inside an encapsulating mass. However, this passive radiofrequency transponder 1′ will be kept away from the ends 932 and 921 of the second 93 and of the fourth 92 layers of elastomer compound so as to preserve the endurance of the tyre casing and the physical integrity of the radiofrequency transponder 1′. Keeping it away from the metal reinforcers of the carcass reinforcement layer improves the communication performance of the passive radiofrequency transponder 1′.
The tyre casing is also equipped with two passive radiofrequency transponders 1ter and 1ter′ in the region of the sidewall 83 of the tyre casing. The first radiofrequency transponder 1ter is positioned at the interface formed by the turn-up 88 of the carcass reinforcement layer and the third layer of elastomer compound 94. The more radially outward positioning of this transponder by comparison with the first two passive radiofrequency transponders 1 and 1′ provides a longer distance for communication with a reader external to the tyre casing, particularly when in service on a vehicle. This first passive radiofrequency transponder 1ter is positioned at least 10 millimetres from the end 881 of the turn-up 88 of the carcass reinforcement layer and at least 5 millimetres from the end 922 of the fourth layer of elastomer compound 92 so as to preserve the endurance of the tyre casing and the physical integrity of the passive radiofrequency transponder 1ter.
Finally, the second passive radiofrequency transponder 1ter′ in the sidewall 83 of the tyre casing is positioned at the interface between the main part 87 of the carcass reinforcement layer and the third layer of elastomer compound 94. This is the best position for the distance for communication between the radiofrequency transponder and an external reader. The distancing of the radiofrequency transponder 1ter′ from the end 911 of the first layer of elastomer compound is 20 millimetres, which is easily enough in this configuration to ensure the endurance of the tyre casing and the physical integrity of the passive radiofrequency transponder 1ter′.
It is preferable to encapsulate the passive radiofrequency transponders 1ter, 1ter′ in an electrically insulating encapsulating mass having a relative dielectric permittivity of less than 10 and of which the extension modulus is less than the extension modulus of the third layer of elastomer compound 94.
In these examples, the first longitudinal axis of the radiating dipole antenna is positioned circumferentially, which for casings of radial tyres ensures that the angle between the first longitudinal axis and the direction of reinforcement of the main part 87 and of the turn-up 88 of the carcass reinforcement layer is at least 60 degrees.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1910570 | Sep 2019 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2020/051649 | 9/22/2020 | WO |
