Method of manufacturing an electronic device for a pneumatic tyre

An electronic device, which is intended to be incorporated into a tire, includes an electronic comprises, a conductor, and a support for the electronic component. The support and the conductor are joined together by a first part for attachment of the support and a second part for attachment of the conductor. A rigidifying casing of the device is overmoulded over at least the first part for attachment of the support and the second part for attachment of the conductor. At least one intermediate transition layer is at least partially overmoulded over the rigidifying casing.

FIELD OF THE INVENTION

The present invention relates to the technical field of tyres.

It is applicable to any type of vehicle tyre. The invention relates more specifically to tyres intended to be fitted to motor vehicles of the passenger car, SUV (sport utility vehicle) or two-wheeled type, for example motorbikes, aircraft, or equally industrial vehicles chosen from vans, heavy vehicles such as metro rolling stock, buses, heavy road transport vehicles, for example trucks, tractors, trailers and off-road vehicles such as agricultural machinery or construction plant or even other transport or handling vehicles.

BACKGROUND

A tyre is manufactured from a collection of semi-finished rubber products in the form of strips, sheets or profiled elements, which may or may not be reinforced, and that are superposed on one another to form a green tyre. Once built, this green tyre is vulcanised in a mould to give a tyre.

The prior art, notably EP 1 858 121, already discloses a tyre containing an electronic device. The electronic device comprises a passive transponder connected to a dipole antenna made up of two strands able to communicate via radiofrequency waves with an external interrogation unit. This type of transponder is generally denoted by the English-language acronym RFID. Such a device is able to store data, for example relating to the identification of the tyre. The electronic device is positioned in the green tyre at an interface between two plies of rubber and is then embedded in the rubber during the vulcanising of the tyre.

The device comprises a PCB (Printed Circuit Board) support comprising a part for attachment of the transponder. The support also comprises an attachment part for each of the strands of the antenna. To manufacture the device, the transponder and one end of each of the two strands of the antenna are positioned on the parts for attachment of the support then the electrical connections are made by soldering these various components together.

Furthermore, once embedded in the rubber of the vulcanised tyre, the electronic device is subjected to local deformations caused by the running of the tyre. These local deformations lead to stresses at the interface. Because of these stresses, the strands break, notably at the joint between the strand and the support. Now, these broken strands have sharp edges or protruding ends which may prove detrimental to the mechanical endurance of the tyre and the safety of the user thereof.

BRIEF DESCRIPTION OF THE INVENTION

It is an object of the invention to improve the mechanical endurance and the user-safety of a tyre containing an electronic device.

To this end, the subject of the invention is an electronic device intended to be incorporated into a tyre, comprising an electronic component, at least one conductor and a support for the electronic component, the support and the conductor being joined together by a part for attachment of the support and a part for attachment of the conductor, the device additionally comprising:a rigidifying casing overmoulded at least over the part for attachment of the support and the part for attachment of the conductor,at least one intermediate transition layer at least partially overmoulded over the rigidifying casing.

Thanks to the protective casing, each conductor is held on the support. The attachment of each conductor is therefore made more reliable. Further, even in the event of failure of the attachment between conductor and support, the casing on the one hand holds these together and on the other hand electrically connects them via the support.

For preference, the casing is made of a material of a rigidity very much higher than that of the rubber of the tyre in which the device is intended to be incorporated. This material is compatible with each conductor and the support can be injection moulded. The material from which the casing is moulded is also compatible with the vulcanising temperature (between 160 and 200° C.) and the curing time (approximately 10 minutes for a tyre for a light vehicle). Further, the material of the casing is compatible with the temperatures at which the tyre will be used (between −40 and +100° C.). Finally, the material does not degrade over time.

The material of the intermediate transition layer has a rigidity that is intermediate between the rigidity of the casing and the rigidity of the rubber of the tyre into which the device is intended to be incorporated. The rigidity is characterized, for example, by the 10% elongation modulus of the material concerned.

In general, an interface between materials having different rigidities forms a critical zone. Thus, as the tyre is driven along, each of the materials the junction of which defines the interface is subjected to stresses. These stresses give rise to different deformations that are dependent on the nature and orientation of the materials of which the junction defines the interface. These differences in deformation cause shearing forces at the interface, hence the critical nature of the interface between these different materials. By reducing these differences the mechanical endurance of the electrical connections between the antenna, the support and the electronic component is therefore improved, thus improving the overall reliability of the device within the tyre.

The intermediate transition layer allows a progressive variation in rigidity between the support and the conductor, the protective casing and the rubber of the tyre. Thus, the smaller the difference in rigidity between the device and the rubber plies, the less critical the interface between the device and the rubber plies becomes.

The intermediate transition layer is made of a material that is not as rigid as the material of the protective casing. This material is compatible with the material of the protective casing, can be injection moulded and is compatible with the curing and service temperatures of the tyre. Finally, this material does not degrade over time.

Advantageously, the rigidifying casing is fully overmoulded over the support and the electronic component.

According to optional features of the device:the elastic modulus of the material of the rigidifying casing is greater than or equal to 1000 MPa.the 10% elongation modulus of the material of the transition layer is between 20 and 80 MPa.

Advantageously, the device comprises at least one interface layer at least partially overmoulded over the intermediate transition layer.

The interface layer further reduces the difference in rigidity between the device and the rubber of the tyre. This then improves the progressiveness of the transition in rigidity between, on the one hand, the electronic component and the conductors and, on the other hand, the rubber of the tyre.

The interface layer is made of a material that is not as rigid as the material of the intermediate layer. This material is compatible with the material of the intermediate layer, can be injection moulded and is compatible with the curing and service temperatures of the tyre. Further, this material is compatible with the rubber of the green tyre and with the vulcanised rubber, notably in terms of adhesion, mechanical properties, and how it evolves over time.

For preference, the 10% elongation modulus of the material of the interface layer is below 10 MPa.

Advantageously, the rigidifying casing comprises means for centering the device in an overmoulding cavity used for overmoulding the intermediate transition layer.

These centering means also provide control over the evenness of the thickness of the intermediate transition layer. Thus, the thickness is constant around the conductor allowing the radiating pattern of the conductor to be uniform and therefore more effective. Further, that makes it possible to provide a progressive transition in rigidity that is consistent for the entire conductor and the electronic component, thus improving the mechanical endurance of the tyre.

Finally, because the casing incorporates the means of centering the device, there is no need to provide external centering means when manufacturing the device.

For preference, the protective casing comprises means of protecting each conductor comprising two lugs arranged in an overall V-shape on each side of the part for attachment of the conductor to the support.

Advantageously, the means of centering the device in the cavity used for overmoulding the intermediate transition layer comprise these lugs. The protection means collaborates with the coating to limit the magnitude of the deformations to which the surrounding rubber is subjected and which are transmitted to the electronic device. The V-shaped geometry provides a progressive limitation of the amplitude. Specifically, the distance between each lug and the conductor increases with increasing distance away from the attachment part and this means that substantial deformations are absorbed far away from the attachment part and smaller deformations are absorbed close to the attachment part. This then reduces the fatigue on the conductor in the part for attachment of the conductor to the support, thus reducing the risks of the conductor breaking.

In one embodiment, the device comprises several intermediate transition layers.

For preference, each intermediate transition layer30has a 10% elongation modulus higher than the 10% elongation modulus of the transition layer it covers.

This then provides a progressive transition in rigidity between the rigidifying casing and the rubber in which the device is intended to be incorporated.

Another object of the invention is a method of manufacturing a device as defined hereinabove, in which:at least the part for attachment of the support and the part for attachment of the conductor are overmoulded,following the step of overmoulding the rigidifying casing, the rigidifying casing is at least partially overmoulded with an intermediate transition layer.

Advantageously, after the step of overmoulding the intermediate transition layer, the intermediate transition layer is at least partially overmoulded with an interface layer.

For preference, the electronic component is attached to a precursor of the support of the electronic component, each conductor is attached to the precursor of the support such that each conductor and the electronic component are electrically connected via the precursor of the support and each conductor is separated from the precursor of the support, the electronic component and the support electrically connecting each conductor and the electronic component.

The method of manufacturing the electronic device is therefore simple and can be automated, thus offering increased reliability at lower cost. Specifically, in order for the electrical connections to be functional, it is necessary for each conductor and the component to be positioned very accurately on the corresponding attachment parts which are electrically connected to one another. It is thus easy to achieve reliable positioning of the electronic component and of each conductor relative to one another because the precursor of the support is designed so that it allows accurate positioning of the precursor of the support with respect to an automatic installation that fits the electronic component and each conductor, thus guaranteeing the relative positioning of each component of the device. Optionally, the precursor of the support incorporates housings for each component, thus improving the positioning of the components.

For preference, the electronic component and each conductor are electrically connected for example by soldering, crimping, clipping or bonding or any other means.

Once the support has been separated from the remainder of the precursor of the support, the component and each conductor are still electrically connected to one another via the support. The support forms a sacrificial part of the support precursor. Finally, the precursor of the support allows the support to be positioned relatively simply in automated means that fits each conductor and the electronic component. Once the electronic component and each conductor have been attached to the support, the support bearing each conductor and the electronic component can be separated from the support precursor.

The support precursor therefore performs a function of positioning the various components relative to one another and a function of electrically connecting them by virtue of the support.

The support also confers rigidity upon the device once it has been separated from the support precursor. Further, the protective casing compensates for the loss of rigidity associated with the separation of the support from the support precursor.

Further, in the device of the prior art, the PCB support generally comprises several layers which, under the effect of stress, separate from one another through delamination. Delamination then leads to electrical malfunctioning of the device of the prior art. By using a support that is not laminated, for example that is a metal monolayer, any potential for delamination of the support is avoided.

Advantageously, the support comprises at least two parts for attachment of the electronic component, the support precursor being designed so that:prior to the separation step, the two parts for attachment of the electronic component are short-circuited via the support precursor, andfollowing the separation step, the two parts for attachment of the electronic component are in open circuit.

In order to afford rigidity to the device and allow relatively accurate positioning of the component and of the conductors, the parts for attachment of the component are connected via the support precursor and are therefore short-circuited before the support is separated.

Once the component and each conductor have been attached to the support and once the latter has been separated, the two parts for attachment of the component need to be in open circuit in order to allow the device to work.

Advantageously, several precursors of several supports are formed by pressing and bending a metal strip.

The present application also relates to a precursor of a support for an electronic device intended to be incorporated into a tyre comprising an electronic component and at least one conductor, and comprising a support comprising:at least one part for attachment of the electronic component;at least one part for attachment of each conductor, which is electrically connected to at least one part for attachment of the electronic component via the support precursor;
the precursor of a support being arranged in such a way that the support can be separated from the support precursor by pressing and/or cutting.

As an option, the support precursor is designed so that:the two parts for attachment of the electronic component are short-circuited via the support precursor when the support is attached to the support precursor; andthe two parts for attachment of the electronic component are in open circuit when the support is separated from the support precursor.

Another subject of the invention is a tyre comprising a device as defined hereinabove.

Advantageously, the 10% elongation modulus of the material of the interface layer is less than or equal to the 10% elongation modulus of the rubber in which the device is embedded.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1depicts a tyre according to the invention denoted by the overall reference P.

In the conventional way, the tyre P comprises a crown S extended by two sidewalls F and two beads B. A single sidewall F and a single bead B are depicted in the figures. The known characteristics of the crown S, of each sidewall F and of each bead B are described in detail in the application published under number FR 2 914 585 and incorporated here by reference. More particularly, the bead B also comprises a device according to the invention, denoted by the general reference10.

FIG. 2depicts the electronic device10according to a first embodiment.

As illustrated inFIGS. 3 and 4, the device10comprises an electronic component12and two conductors14, in this instance two antennas14, forming a dipole. The electronic component12comprises a chip16of RFID type comprising pins18for attachment of the chip16to a support20of the device10. Each conductor14is substantially rectilinear and has a helical shape defining the axial direction X of the device10. The figures depict mutually orthogonal axes X, Y, Z corresponding to the axial (X), transverse (Y) and vertical (Z) orientations of the device10.

The support20, which has been separated from a precursor22of the support20, comprises two parts24A,24B for attachment of the electronic component12to the support20and two parts26A,26B for attachment of each conductor14to the support20. Each conductor14comprises a proximal part14A for attachment of each part26A,26B and a radiating distal part14B. Each conductor14and the support20are connected by the parts14A and26A,26B. Each part26A,26B is electrically connected to each part24A,24B for attachment of the electronic component by a joining part27of the support20. The two parts24A,24B for attachment of the electronic component12are in open circuit when the support20is separated from the support precursor22.

With reference toFIG. 5, the device10comprises a rigidifying casing28. The casing28is overmoulded directly onto the electronic component12, the conductors14and the support20. In this particular instance, the casing28completely and directly overmoulds the electronic component12, the support20, each attachment part24A,24B,26A,26B, each joining part27and each proximal part14A for attachment of each conductor14. In particular, the casing28is overmoulded over the junction formed by the parts26A,26B for attachment of the support20and the part14A for attachment of each conductor14.

As depicted inFIGS. 2 and 6, the device10comprises at least one intermediate transition layer30and one interface layer32for interfacing with the rubber of the tyre in which the device10is embedded. In this particular instance, the device10comprises a single intermediate layer30. The intermediate layer30is overmoulded directly onto the casing28and onto each distal part14B of each conductor14. The intermediate layer30in this instance is fully overmoulded onto the casing28. As an alternative, the device10comprises several intermediate transition layers30. The interface layer32is overmoulded directly onto the outermost intermediate layer30. The interface layer32here is completely overmoulded over the transition layer30.

As illustrated inFIG. 5, the casing28comprises means34for centering the device10in a cavity used for overmoulding the intermediate layer30. The intermediate layer30also comprises means36for centering the device10in a cavity for overmoulding the interface layer32. The casing28finally comprises means37for protecting each conductor14.

The means37is combined with the means34. Specifically, the means34and37comprise lugs38arranged in an overall V-shape transversally on each side of each attachment part26A,26B. These lugs38provide for the axial and transverse positioning of the casing28and therefore of the device10in a cavity used for overmoulding the intermediate layer30. The means34further comprises end stops40arranged on the casing28vertically on each side thereof.

The means36comprises end stops42overmoulded onto each part14B of each conductor14and lugs44overmoulded onto the casing28.

The casing28is made of a thermosetting plastic based, for example, on epoxy resins, on liquid crystal polymers (LCP) or on polybutylene terephthalate (PBT). This casing28is highly rigid, something that is made possible by virtue of the use of these thermosets. The crosslinking can be carried out during and/or after the operation of injecting the casing overmoulding material without the need for post-curing. Following complete crosslinking and separating of the support20from the support precursor22, the casing28needs to be able to withstand all the mechanical stresses experienced by the device when the tyre is in use without appreciable deformation in order to guarantee correct electronic operation of the electrical connections between the electronic component12, the conductors14and the support20. The elastic modulus of the material of which the casing28is made is greater than or equal to 1000 MPa.

Each intermediate layer30and interface layer32is preferably made of a thermoplastic material such as thermoplastic elastomers or TPEs, for example styrene/butadiene (SB), styrene/butadiene/styrene (SBS), styrene/isoprene (SI), styrene/isoprene/styrene (SIS), styrene/isoprene/butadiene/styrene (SIBS), styrene/ethylene/butylene/styrene (SEBS), styrene/ethylene/propylene/styrene (SEPS), styrene/ethylene/ethylene/propylene/styrene (SEEPS) block copolymers, thermoplastic polyurethanes (TPU), TPV such as PP/EPDM-VD, and blends thereof. These materials need to be chemically compatible with and adhere well to the adjacent materials.

Each material of each transition layer30has a 10% elongation modulus of between 20 and 80 MPa. When the device10comprises several transition layers30, each transition layer30has a 10% elongation modulus that is higher than the 10% elongation modulus of the transition layer30that it covers or overmoulds.

The 10% elongation modulus of the material of the interface layer32is less than or equal to the 10% elongation modulus of the rubber in which the device10is embedded. By way of example, the 10% elongation modulus of the material of the interface layer32is between 1 and 10 MPa. When the device10is positioned in a bead, as is the case of the tyre P ofFIG. 1, the 10% elongation modulus of the material of the interface layer32is less than or equal to 5 MPa. When the device10is positioned in a sidewall, the 10% elongation modulus of the material of the interface layer32is less than or equal to 2 MPa.

A method of manufacturing the device10according to the invention will now be described with reference toFIGS. 7 to 12.

Use is made of a metal blank46, for example in the form of a strip of surface-treated brass as illustrated inFIG. 7.

The method is implemented using an installation48for manufacturing the device10, which installation is depicted in part inFIG. 8. The installation48comprises means (not depicted) for guiding the strip46. The guide means comprises two guideways in which the strip46is slid.

The installation48also comprises pressing means (not depicted) exhibiting a pressing pattern by means of which the strip is periodically pressed. The installation48also comprises means for bending and folding the strip46(this means has not been depicted).

The installation48also comprises means54for centering and driving the strip with respect to the installation48. The means54comprises pins56aligned substantially in the middle between the two guideways.

Finally, the installation48comprises an injection mould58for injection moulding the casing28and means for cutting the support20(this means has not been depicted). The injection mould58notably comprises a cavity59for moulding the casing28.

The strip46is pressed using the pressing means to yield a pressed strip60. This pressed strip60comprises several precursors22for several supports which are identical and joined together by joining portions62.

With reference toFIG. 9, each support precursor22comprises a rectangular surround64comprising four branches64A-D that are parallel in pairs. Two branches of the surround, in this instance the branches64A,64C, are joined together by a middle branch66which is hollowed at its middle and is substantially parallel to the branches64B,64D. The support precursor22also comprises the support20which comprises the two parts24A,24B for attachment of the electronic component12and the two parts26A,26B for attachment of each conductor14. InFIG. 9, the attachment parts26are still flat and the two parts24A,24B for attachment of the electronic component12are short-circuited via the support precursor22because the support20is secured to the support precursor22. In addition, the support precursor22comprises means68for centering each support precursor22in the installation48. The means68complements the means54and comprises two orifices70formed at the intersection between each branch64A,64C and the middle branch66.

With reference toFIG. 10, during a step subsequent to the pressing step, each part26A,26B is folded to make a channel72. The surround64is also bent so that the support20is raised up in relation to the branches64B,64D when the support precursor is resting on the branches64B,64D.

With reference toFIG. 11, the electronic component12and each conductor14are attached respectively to the parts24A,24B and26A,26B of the support20. In this particular instance, a brazing paste is applied to each part24A,24B,26A,26B then each conductor14and the electronic component12are set in place and the brazing paste is melted to attach and electrically connect each conductor14and the electronic component12during a reflow soldering step.

With reference toFIG. 12, the electronic component12, the support20and each proximal part14A for attachment of each conductor14are overmoulded with the casing28using the mould58.

Next, the support20bearing the component12, the conductors14and the casing28is separated from each support precursor22by cutting and/or pressing the support20, in this instance each middle branch66transversely on each side of the device10. This then yields an intermediate device10as depicted inFIG. 5.

Each intermediate device10ofFIG. 5is positioned in a mould for injection moulding the intermediate layer30and the layer30is overmoulded onto the intermediate device10ofFIG. 5. This then yields the intermediate device ofFIG. 6.

Next, each intermediate device10ofFIG. 6is positioned in an injection mould for injection moulding the interface layer32and the layer32is overmoulded onto the intermediate device10ofFIG. 6. This then yields the device10ofFIG. 2.

FIG. 13depicts a device10according to a second embodiment. Elements that are analogous to those depicted in the preceding figures are denoted by identical references.

In contrast to the first embodiment, the means36for centering the device10in the cavity used for overmoulding the interface layer32is not borne by the intermediate layer30but are borne by the mould. This means36notably comprises pairs of half-shells (not depicted) for positioning the intermediate device coated with the intermediate layer in the cavity used for moulding the layer32. Once the device10has been removed from the mould, notches74remain, along each distal part14B of each conductor at the points at which the positioning shells had been located. Of course, these notches no longer remain when the positioning means is retractable. In this embodiment, the layer30therefore does not necessarily have the lugs42.

FIGS. 14A-Cdepict various embodiments of the support20. Elements analogous to those depicted in the previous figures are denoted by identical references.

InFIG. 14A, each attachment part26A,26B has several tongues76for holding each conductor14on each attachment part26A,26B.

InFIG. 14B, in addition to the tongues76of the embodiment ofFIG. 14A, the support20comprises at least one upstand78for protecting the electronic component12, in this instance two upstands positioned transversely one on each side of each part24A,24B. Further, the support20comprises projections80for supporting each lug38.

InFIG. 14C, in addition to the two parts26A,26B for attachment of the electronic component12, the support20comprises a central support part82of the electronic component12which part is arranged between the two parts26A,26B and electrically insulated from each part24,26when the support is separated from the support precursor22.

The invention is not restricted to the embodiments previously described.

Specifically, the features of the various embodiments of the support20can be combined indifferently.

Further, the bending step may be done prior to the folding step, and vice versa.

In addition, the device10may comprise more than three layers in order to improve the transition in rigidity between the electronic component12, the conductors14and the rubber of the tyre.

The electronic component12may be of the passive type, which means to say one capable of communicating data contained in an electronic chip to an external interrogation unit, or may be of the active type, which means to say one capable of receiving data emitted by a sensor in order to communicate it to an external interrogation unit. Such an active component may notably contain a microprocessor and a memory.