WO2020120923A1

WO2020120923A1 - Model for predicting wear and the end of life of a tyre

Info

Publication number: WO2020120923A1
Application number: PCT/FR2019/053088
Authority: WO
Inventors: Anne-Laure FRAENKEL; Richard Abinal; Nicolas DELIAS; Vincent Dubourg
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2018-12-14
Filing date: 2019-12-16
Publication date: 2020-06-18

Abstract

A method for estimating the overall wear of a tyre having a crown, the crown comprising a tread having a mean thickness E, the tyre delimiting an internal cavity, comprises the following steps of: -obtaining a transfer function F of the tyre over reference ground depending on influencing factors and on the thickness E; -obtaining a passage function β of the mounted assembly, which function is defined for a section of road; in a measurement cycle -determining a force FX and a rate of slip g% at the wheel centre of the tyre, when running in a straight line with variations in acceleration over the section of dry road; -determining a load Z1 to which the mounted assembly is subjected; -determining a temperature T1 of the mounted assembly; -determining an inflation pressure P1 of the internal cavity.

Description

DESCRIPTION

TITLE: MODEL FOR PREDICTING WEAR AND END OF LIFE

OF A TIRE

Field of the invention

The present invention relates to a method for estimating wear on a global scale as well as a method for predicting the end of life of a tire in conditions of use on a vehicle and a system for implementing these. methods.

Technological background

[0002] In the field of methods for evaluating the wear of a tire in conditions of use on a vehicle, it is frequently considered that a simple and easy way to determine it is to evaluate the corresponding overall wear the average decrease in the height of the tread. To this end, it is commonly envisaged to use an intermediate physical quantity sensitive to the wear of the tread of a tire such as, for example, the tread radius Re or the longitudinal stiffness Kcc. This second quantity represents the slope of the curve representing the longitudinal forces Fx generated by the variation in rotational speed w between the wheel center and the tread when the assembled assembly is traveling on the road. The sensitivity of the longitudinal stiffness is much stronger to the overall wear of the tire casing than the sensitivity of the rolling radius.

Known in the prior art, in document US607035A, methods employing such a second quantity to characterize the overall wear of the tread of the tire in service. This quantity is in fact sensitive to the reduction in the height of the tread characterizing the overall wear of the tire.

However, this physical quantity is also sensitive to other parameters such as the inflation pressure, the temperature, the load carried by the assembled assembly, the nature of the ground on which the assembled assembly rolls. Variations in all of the influencing parameters must therefore be taken into account in order to extract the variation in longitudinal rigidity due solely to the reduction in the height of the tread of the tire. To do this, the recommended solutions consist in taking into account the variations of these influencing parameters through additional measurements or additional information. If this seems fairly easy in terms of temperature or inflation pressure of the tire by means of direct measurements, the task is much more delicate in terms of the nature of the soil or other influencing parameters. Of course, the fact that an influential parameter is not taken into account leads to an error being made in the evaluation of the overall wear of the tire.

The present invention aims to provide solutions to take into account all of the influencing parameters and in particular the nature of the soil in order to be more precise on the estimation of overall wear and the prediction of end of tire life. Description of the invention

The invention relates first of all to a method of estimating the overall level of wear of a tire of an assembly mounted in running condition on a vehicle. The tire has a crown which is extended by two sidewalls ending in two beads, of revolution around a natural axis of rotation. The crown comprises a tread located radially outside the tire with respect to the natural axis of rotation having an average thickness E. The assembled assembly comprises components, including a wheel and the tire, delimiting an internal cavity. The estimation method comprises the following steps: - Optionally, obtaining an identification of the at least one component of the assembled assembly, preferably the pneumatic envelope;

Obtain a transfer function F of the assembly mounted between a longitudinal stiffness Kxx ^ref on a reference soil and influencing factors, such as being the product of a first function F1 having as influencing factors at least the inflation pressure P, the temperature T and the load Z undergone, by a second bijective function F2 having at least as factor influencing the thickness E of the strip of rolling ;

Obtain a function of passage b of the assembled assembly defined for a portion of road as being the ratio of the longitudinal rigidities Kcc of F assembled assembly with iso influencing factors of which that in the numerator is evaluated on a ground equivalent to the portion of road and that in the denominator is evaluated on a reference soil;

On the same measurement cycle:

Determine at least one effort Fx undergone by the assembled assembly and at least one slip rate g% at the wheel center of the assembled assembly, or obtain the vehicle parameters Ql allowing their determination, when running in a straight line from the vehicle having variations in acceleration on said portion of road, the latter being dry;

Determine a load ZI undergone by the assembly assembled in running condition or the parameters Q2 of the vehicle allowing its determination;

Determine a temperature Tl of the assembly assembled in running condition

Determine an inflation pressure PI of the internal cavity of the assembly assembled in running condition.

The method is characterized in that it comprises obtaining a first longitudinal stiffness Kxx ^reel of the assembly mounted on real ground using a first relationship linking the force Fx and the slip rate g% or the parameters Ql, in that it includes obtaining a second longitudinal stiffness Kxx ^ref on the reference ground evaluated using the transfer function F supplied by at least the influencing factors Tl, PI, ZI or the parameters Q2, and at least one characteristic thickness E0 of the tread, in that it includes obtaining a scalar bi defined using the passage function b supplied by at least the influencing factors Tl, PI, ZI and in that the thickness E of the tread is determined by a second relation linking the scalar bΐ, the first longitudinal stiffness Kxx ^reel and the second longitudinal stiffness K _xx ^ref in the following way:

The term “measurement cycle” is understood here to mean that the assembled assembly is in iso condition of use for parameters such as the inflation pressure P, the temperature T and the load Z undergone. Of course, the term iso is understood to mean that the variations of these parameters during the measurement cycle are insignificant compared to the average value of these parameters over the entire measurement cycle. In addition, the wear E of the tread and any other influencing parameter associated with the state of the mounted assembly are considered to be invariant during the same measurement cycle. Indeed, the measurement cycle has a duration much less than the duration necessary to observe a variation in the state of the assembled assembly.

The term "assembly cycle state" is understood here to mean that the influential parameters of a second group H such as the thickness of the tread are constant over the duration of the cycle. On the other hand, the parameters of a first group G related to use can vary over the duration of this cycle.

[0009] The term “obtaining data” means here that this data is defined by a measurement, an estimate or that this data is determined on a lump sum basis.

Therefore, it is necessary that the determination of the various parameters of the mounted assembly is carried out in a short period corresponding to the measurement cycle. All the means of the state of the art respecting this constraint can be used. Thus, the pressure PI and temperature Tl measurements will conventionally be obtained by direct or indirect sensors. By way of nonlimiting example, a pressure sensor in fluid communication with the internal cavity of the mounted assembly is a direct measurement of the inflation pressure. On the other hand, a temperature sensor of the fluid contained in the internal cavity is an indirect measurement of the temperature of the mounted assembly and in particular of the tread of the tire. The use of a thermal model taking into account the heat exchanges between the various components (internal fluid, components of the assembled assembly and external fluid) and according to the various modes of transmission (radiation, convection, conduction) is necessary. Of course, a measurement by means of a thermocouple implanted in the tire is a more direct measurement of the temperature, but it is difficult to implement since this requires a structural modification of the tire envelope.

These sensors are conventionally packaged in electronic systems fixed to the assembled assembly such as for example TPMS (acronym in English of Tire Pressure Monitoring System) mounted on the valve or TMS (acronym in English of Tire Mounted Sensors) fixed on the internal wall of the tire delimiting the internal cavity.

With regard to the load on the mounted assembly, various measurement techniques are possible. Initial estimates based on the assessment and the distribution of the overall static load of the vehicle can be used. In addition, the static mass of the vehicle can be adjusted by vehicle indicators included in the group comprising the fuel level, the seat belt latch, the trim of the vehicle, the state of compression of the shock absorbers. In this case, a set of vehicle parameters Q1 is used.

More direct measures at the level of the assembled assembly can also be envisaged. For example, the calibration of a periodic signal around the wheel makes it possible to extract a longitudinal dimension, characteristic of the contact between the pneumatic envelope and the ground for a given mounted assembly. In this case, a sensor sensitive to the radial and / or longitudinal deformation of the tire of the type, for example, accelerometer or piezoelectric element is envisaged. The use of charts between this characteristic dimension and the inflation pressure P makes it possible to go back to an evaluation of the load Z undergone by the assembled assembly.

Of course, other devices can also be used. By way of nonlimiting illustrative example, it will be noted that the processing of at least two measures of circumferential extension or contraction in at least one side of the envelope at two fixed points in space, located at different azimuths along the circumference makes it possible to estimate the forces at the wheel center. This contraction or circumferential extension of the flanks is advantageously estimated by measuring the distance between the wires of the carcass ply of the flanks. Reference will be made to patent document WO-A-03/014693 in the name of the applicants for a detailed description of this measurement of the characteristics of the assembled assembly.

Finally, for the measurement of longitudinal stiffness Kcc, this requires both measuring the forces Fx at the wheel center of the assembled assembly and the slip rate g% of the assembled assembly relative to the actual ground. . Thus, it is necessary to obtain reliable information of these two quantities in real time.

For the longitudinal forces Fx at the wheel center of the mounted assembly, these can be estimated, for example, through the torques applied around the axis of rotation of the mounted assembly, whether they are motors or brakemen. This implies being able to trace this data through the characteristics of the vehicle.

They can also be obtained through the static load of the vehicle and the longitudinal acceleration of the center of gravity of the vehicle coupled to the distribution of the engine and braking forces between the front and rear axles. Optionally, the physical model making it possible to go back to the longitudinal forces Fx at the wheel center of the mounted assembly takes into account various parameters Q2 including the slope of the road, the forward speed of the vehicle, the aerodynamic drag of the vehicle and the resistance to tire casing roll. Finally, more direct measurements at the level of the mounted assembly can also be envisaged to evaluate the efforts of the wheel center Fx. It will be noted by way of nonlimiting illustrative example that the processing of at least two measures of circumferential extension or contraction in at least one side of the envelope at two fixed points in space, located at different azimuths on along the circumference allows to estimate the forces in the wheel center. This contraction or circumferential extension of the flanks is advantageously estimated by measuring the distance between the wires of the carcass ply of the flanks. Reference will be made to patent document WO-A-03/014693 in the name of the applicants for a detailed description of this measurement of the characteristics of the assembled assembly.

The other essential characteristic for the evaluation of the longitudinal stiffness Kcc is the slip rate g% of the assembly mounted in the wheel center. This quantity can be estimated directly by the data supplied by the electronic systems on board the vehicle such as the ABS system. It can also be evaluated through three basic parameters which are the speed of rotation W of the assembly assembled at the wheel center, the rolling radius Re of the assembly assembled and the forward speed V0 of the vehicle.

The speed of rotation W can be simply obtained by a wheel encoder coupled to a clock. The rolling radius Re of the mounted assembly, which is not very sensitive to wear, is obtained using the distance traveled by the vehicle and the number of revolutions made by the mounted assembly to cover this distance. Finally, the forward speed V0 of the vehicle is obtained by means of a high-frequency measuring device of the RT 3000 type for example to have sufficient accuracy.

Finally, the overall wear of the tire is evaluated in real time by the almost simultaneous determination of the parameters of the mounted assembly, which are the conditions of use, influencing the longitudinal stiffness Kcc of the mounted assembly and the parameters condition of the mounted assembly and in particular of the tire which have been determined over a possibly longer period. In particular it is necessary to take into account the influence of the nature of the soil through an indicator, the scalar bΐ defined using the passage function b. Unlike the solutions proposed in the prior art, the chosen indicator is not constructed solely on the basis of soil macroroughness information. But above all, the indicator is also linked to the assembled assembly and in particular its interaction with the ground which is expressed through the rigidity of the tread of the tire which is the structural element of the tire in contact with the ground. Thus, the passage function b and consequently the scalar bΐ are defined using the longitudinal rigidity of the mounted assembly and they are linked to the mounted assembly. Of course, the passage function b is also linked to the portion of the road characterized by its geographic location through, for example, GPS data. However, we can take a flat-rate function for this quantity b knowing the sensitivity of the longitudinal rigidity Kxx of the assembled assembly according to the nature of the ground, according to the condition of the tire and to an estimate of the nature of the real ground of the portion of road. Taking into account the interaction between the ground and the assembled assembly is a key factor for quality identification of the thickness E of the tread. The identification of the passage function b of the assembled assembly is obtained by a campaign of experimental characterizations and / or numerical simulations. A series of characterizations is created for this by understanding the longitudinal rigidities of the assembly mounted to these iso influencing factors between the soil to be characterized and a reference soil. The passage function b potentially depends on influencing factors linked to the use of the assembled assembly, such as the inflation pressure P, the temperature T and the load Z undergone by the assembled assembly.

In addition, the transfer function L on reference ground is an intrinsic datum to the assembled assembly. This makes it possible to properly dissociate the variations in longitudinal rigidity due to the usage parameters, such as the pressure P, and state, such as the wear of the tread, of the assembled assembly independently of those generated by the parameters related to the roadway in general. Furthermore, the identification of this transfer function L can be carried out under conditions metrological expertise. Knowledge of the soil and the conditions of use and condition, including the load is essential to a precise identification of this transfer function F. Thus better accuracy in estimating the average thickness E of the tread is reached regardless of the interaction with the actual soil.

Finally, the identification of the overall wear of the tire is carried out during driving without the need for a stop to perform a manual inspection or structurally modify the tire to interrogate it by means of non-contact measurements. As a result, the process is neither intrusive in relation to the pneumatic product, nor restrictive for the user of the vehicle.

Preferably, the transfer function F of the mounted assembly depending on the aging D of at least one of the components of the mounted assembly, the method comprises determining the aging DI of the at least one component of the assembled assembly in the same state cycle of the mounted assembly and obtaining the second longitudinal stiffness Kxx ^ref is carried out by using the aging DI of at least one component of the mounted assembly.

The aging D of the components of the mounted assembly and very particularly those comprising materials based on an elastomeric mixture such as the tire has a non-negligible influence on the longitudinal stiffness Kcc of the mounted assembly. Indeed, the aging of these materials modifies the rigidity of the components associated with these materials. This influences the value of longitudinal rigidity of an assembly mounted between two aging states of this same assembled assembly. As a result, aging is also an influencing factor. However, aging is linked to the state cycle of the assembled assembly and not to the measurement cycle. Therefore, it is an influencing factor of the longitudinal stiffness Kcc of the second group H linked to the state of the assembled assembly. Consequently, the determination of the aging of the components of the assembled assembly is to be performed less frequently than the factors of the first group of influencing factors. According to a particular embodiment, the aging DI of at least one component of the assembled assembly is determined by at least one of the quantities included in the group comprising the age, the overall mileage covered or the number of cycles performed , the history of the overall mileage traveled or of the cycles performed, the cumulative thermomechanical stress experienced, the history of thermomechanical stresses experienced, the cumulative environmental condition defined by the parameters included in the group including ambient temperature, humidity, level ozone and the history of environmental conditions suffered.

As a first approximation, the aging of a component, in particular those comprising elastomeric mixtures, is similar to the age of the structural components of the mounted assembly which can be entered in the vehicle data.

In fact, the aging of the assembled assembly and in particular that of the tire can be evaluated using one or more parameters from the preceding list. The most basic model is to take into account only the age of the tire through its date of manufacture. This data is accessible via identification vectors present on the components themselves such as bar codes, QR codes or any other physical vector. In addition, some physical vectors are electronic objects commonly known as RFID (acronym for Radio Frequency Indentification) which can contain the information and communicate it by radio frequency on request.

Another elementary model would be to take into account the overall mileage covered or the number of cycles performed by the latter. A specific model of aging of the components of the assembled assembly and in particular of the tire or of products based on an elastomeric mixture would be to take into account the history of the thermo mechanical stresses undergone by the component and in particular the history of the temperature. during operation and during storage of the component. It should be noted that here the aging of the assembled assembly results in the evolution of these physical characteristics, such as rigidity for example, which is particularly visible on the structural components of the assembly mounted on the basis of an elastomeric mixture.

Advantageously, obtaining the transfer function F, and in the same way, obtaining the passage function b, is carried out through a characterization campaign included in the group comprising numerical simulation and measurements experimental.

This transfer function F, and also the passage function b, requires evaluations of longitudinal stiffness Kcc of the assembly mounted on the same reference ground. These evaluations can be carried out experimentally on the same floor by varying the various influencing parameters either using a means of displacement of the assembly mounted such as a vehicle or a trailer or on a measurement bench. Likewise, these assessments can be simulated numerically by modeling, for each assessment, the same reference soil. This second option is inexpensive when Fon has to perform the transfer functions F for the entire dimensional range of a tire model or for various mounted assembly components. Of course, it is possible to mix the two types of characterizations in order to first validate a numerical model on a tire dimension or a particular mounted assembly and then extend the characterization numerically on the dimensional range of the tire or variants of the components of the assembled assembly.

Very advantageously, the transfer function F is obtained on a macrolisse soil.

The term "macrolisse soil" is understood here to mean the specific characteristics of a soil on a scale of the order of a millimeter. These specific characteristics are thresholds from which the soil is considered to no longer represent roughness on this scale. If we take as characteristic the PMT (acronym of Average Texture Depth) by a volumetric measurement according to the NF standard EN 13036-1, the characteristic can be the average diameter of the circle formed by the glass balls calibrated by the method for an elementary quantity of these balls or the quantity of balls deposited then leveled to form a circle with a diameter 0.2 meter determined on this ground. We can also take as an indicator of the roughness of the soil, the PMP (acronym of Average Profile Depth) according to standard NF EN 13473-1. Finally, it is also possible to consider as an indicator of the macroroughness of the soil the average diameter of the indenters and / or their spatial density and / or their height obtained by a three-dimensional profiometric measurement of the soil as illustrated in application FR2948764A1 of the Applicant, the macroroughness of the soil will be a density of indenters greater than Densmax, an average diameter of these indenters less than Diammin and an average height less than Hautmin. The identification of these various thresholds can be obtained by applying the methods for characterizing the macroroughness of the soil on an adhered soil of type 120 from 3M or 180 from Norton considered as macrolisse by way of example.

Indeed, if the soil has a low macroroughness, the longitudinal stiffness Kcc of the assembled assembly is maximum. This then makes it possible to have a stronger response dynamic in the variations of the influencing parameters thus facilitating the identification of the transfer function F. In addition, the numerical simulation of a smooth or macrolisse soil is elementary making it possible to optimize the computing time in digital simulation. However, in an experimental campaign, in particular on a flattrack type test bench for example, the use of an adhered film on the metal track reproducing the smooth ground is necessary to obtain a certain level of adhesion in the contact zone between the tire tread and the flywheel of the measurement bench.

Preferably, the transfer function F is obtained by using a mathematical model of the type:

Or

M ^J o and E _ref , are constants:

a, _j , and a are reals;

M ^J are influencing factors;

E is the thickness of the tread

This form of transfer function is suitable for calibrating the experimental results, it makes it possible to cover a wide range of values for all of the influencing parameters instead of focusing around a nominal position by means of limited development for example. In addition, the influencing parameters are here independent of each other, thus facilitating the identification of the parameters of the transfer function F. Finally, this transfer function is focused on the interaction of a single soil, the reference soil, with the assembly mounted. It is considered that this sensitivity of the longitudinal rigidity Kcc to this coupling between the assembled assembly and the various soils is integrated only in the passage function b.

According to a particular embodiment, obtaining the passage function b comprises the following steps:

- Carry out a set of measurement cycles associated with various road sections, the road sections being dry, in the same state cycle of the assembled set;

Obtain for each measurement cycle the first longitudinal stiffness kxx ^reel on real ground and the second longitudinal stiffness k'xx ^ref on reference ground;

Obtain for each measurement cycle a difference X between the first and the second longitudinal stiffness; Define a target measurement cycle among all of the measurement cycles by identifying the one with the smallest deviation X;

Assign the identity function to the passage function b defined for the road portion associated with the target measurement cycle.

This is a special case of using the method where the transfer function F is evaluated on a macrolisse soil. Thus, by seeking in the same usage cycle of the assembled assembly, the portion of road corresponding to the smallest difference between the first and the second longitudinal rigidity, it is possible by multiplying the longitudinal stiffness measurements to stretch strongly or even reach a portion of road where this difference will be zero corresponding to a smooth macro soil. The probability of 100% will be reached for an infinite number of stiffness measurements on a set of road sections representative of the diversity of soils. Thus, the passage function b for this assembly mounted on this portion of road minimizing the deviation X also tends towards identity. The identification of the thickness E of the tread is directly obtained by the identification of the influential parameters of the first group G.

By the identity function here is meant that whatever the parameter set of the function, here the passing function b, the latter always returns the same result, here a scalar bΐ which is equal to one.

Of course, it is important to associate with the passage function b defined for this portion of road, the geographic location of this portion of road in order to be able to reuse this quantity intrinsic to the pavement in future evaluations of the tire wear. Generally, the location of this portion of road is obtained through the GPS data delivered by the vehicle.

According to a preferred embodiment, obtaining the passage function b comprises the following steps:

- Obtain an average thickness E2 of the tread;

- Carry out a measurement cycle associated with a road section, said road section being dry in the same state cycle of the assembled assembly - Obtain the first longitudinal stiffness kxx ^reel on real ground;

- Obtain a third longitudinal stiffness k ”xx ^ref on reference ground evaluated using the transfer function F supplied with parameters including the influential parameters obtained during the measurement cycle and the thickness E2 of the tread;

- Obtain a coefficient l as the ratio of the first longitudinal stiffness kxx ^reel on real soil to the third longitudinal stiffness k''xx ^ref on reference soil;

- Determine the passage function b associated with the portion of road passing through the point (l, PI, Zl, Tl) associated with the measurement cycle.

Thus, whatever the height E of the tread of the tire, that is to say total or partial, it is possible to identify the passage function b associated with a portion of road suitable for longitudinal stiffness measurement on vehicle by using the transfer function F of the mounted assembly. This evaluation of the height E of the tread can be obtained by an estimate such as for example when the tire has not yet rolled slightly or by a measurement through a spot measurement using an instrument manual or indirect metrology via an electronic device such as a scanner drive over.

Of course, it is important to associate with the passage function b of this second portion of road, the geographical location of this second portion of road in order to be able to reuse this quantity intrinsic to the pavement in future evaluations of the wear of the tire or other tires. Generally, the location of this second portion of the route is obtained through the GPS data delivered by the vehicle.

According to a third preferred embodiment, obtaining the passage function b comprises the following steps:

- Obtain a passage function b2 of the assembled assembly defined for a second portion of the road; - Obtain for the soil of the second portion of the road a vector M2 characterizing the macroroughness of the soil relative to a reference soil;

- Obtain for the soil of the road portion a vector M characterizing the macrorugosity of the soil relative to a reference soil;

- Determine the passage function b of the assembled assembly defined for the road portion by a relation linking the passage function b2 and the relative position of the vector M2 with respect to the vector M.

The term "macroroughness" is understood here to mean the structural characteristics of the soil on a scale of the order of a millimeter. Each characteristic represents a variable of the vector M associated with the overall macroroughness of the soil. Of course, the vector can be limited to a scalar representing for example the PMT (acronym of Average Texture Depth). It can also be an n-dimensional vector if we take into account a certain number of descriptors of the soil macro-roughness such as the number of indenters per unit area, the average radius of these indenters and the average height of these.

According to a preferred embodiment, the method for estimating the overall wear level comprises the additional steps:

- Determine a variation AU between at least two thicknesses E of the tread of at least one parameter U linked to the use of the tire included in the group comprising rotation cycles carried out, kilometers traveled, time, time of use of the tire ;

- Determine at least one overall speed V of tire wear defined by the ratio between the variation DE of the thickness between the at least two thicknesses E of the tread and the variation AU of the at least one parameter U linked to l use of the tire.

Although the estimate of the overall wear of the tire is essential, it is necessary to determine the overall wear rate of the tire in order anticipate, if necessary, a level of tire wear during a future estimate. This makes it possible to enrich the global wear estimation model if necessary by improving, for example, the identification of the passage function b. Indeed, the passage function b is dependent on the nature of the ground but also on the rigidity of the tread of the tire which will impact the interaction between the assembled assembly and the ground. However, the rigidity of this component of the tire depends both on the characteristics of the materials constituting it but also on its geometry and very particularly on its thickness.

Of course, this overall wear speed is a function only of the variation both of the thickness E of the tread between two states of the tire and of the variation of a parameter related to the use of the tire. Among the most relevant parameters related to the use of the tire, the number of cycles carried out or the mileage traveled between the two estimates of the thickness E can be advantageously coupled with the total duration or the simple duration of use of the tire between the two estimates of thickness E.

The invention also relates to a method for predicting the end of life of a tire having a tread located radially outwardly relative to a natural axis of rotation of the tire, having an average thickness E, a characteristic thickness E0 and an end of life thickness E ^end , comprising the following steps:

- Determine at least a thickness El of the tread of a tire during at least a first tire condition cycle of a first mounted assembly comprising said tire by using the wear estimation method overall of a tire;

- Determine a speed VI of overall wear of the tire associated with the at least one thickness El using the method of estimating the overall wear of a tire; - Determine a value U1 of the parameter U linked to P use of the tire, associated with the at least one thickness El;

- Determine the end of life prediction of the tire using a value U ^fm of the parameter U defined by a second function linking the overall wear speed VI, the at least one thickness El associated with the value U 1 and l thickness end of life E ^end .

A first estimate of the end of life prediction of the tire is determined through a value U ^fm of the parameter describing the use of the tire. By extrapolating the overall wear speed VI attached to an estimate El of the thickness of the tread with which is associated a value U1 of the parameter linked to the use of the tire, it is possible to identify a value U ^fm corresponding to the threshold value of the parameter U linked to the use of the tire.

Of course, the closer the end-of-life prediction is made to the value U ^fm , the more the quality of the prediction is improved. However, this method makes it possible to regularly inform the user of the vehicle or an intermediary of the potential for using the tire.

The speed of calculation of the end-of-life prediction associated with the simplicity of implementation of the method of predicting the overall wear on which it is based gives a certain interest to this method for planning and organizing maintenance operations. of the vehicle regarding tire wear.

The invention also relates to a system for implementing the method for estimating the overall wear level of a tire and / or the method for predicting the end of life of a tire, comprising:

- a vehicle equipped with at least one mounted assembly comprising said tire that can be put into driving condition;

- a means of storage,

- a means of calculation, an analysis means, a first means of transmission between the vehicle and the at least one storage means, a second means of transmission between the at least one storage means and the at least one calculation means,

- a third means of transmission between the means of analysis and the means of storage or the means of calculation,

- input data from the vehicle,

- intermediate data stored in the storage means which can be transmitted by an external system,

- an output result from the calculation means, and

- a decision from the means of analysis.

The input data are included in the group comprising the load Zl, the temperature Tl, the pressure PI, the force Fx, the slip rate g%, the parameters Q1 and Q2, the parameter U linked to the use of the pneumatic and the variation AU of the parameter U. The intermediate data are included in the group comprising the thickness E2, the aging DI of the component of the assembled assembly, the characteristic thickness E0 and the thickness end of life E ^end of the tire tread, the transfer function F of the assembled assembly, the passage function b of the assembled assembly associated with the road portion, the vector M characterizing the macroroughness of the soil of the road portion relative to a reference soil. The output result is included in the group comprising the thickness E of the tread of the tire, the overall wear speed V of the tire, the end of life prediction U ^fm of the tire associated with the parameter U, the first stiffness longitudinal Kxx ^reel , the second longitudinal stiffness Kxx ^ref , the third longitudinal stiffness k ”xx ^ref . The decision expressing the state of wear of the tire is transmitted and / or stored in the storage means using a fourth transmission means.

This system makes it possible to set up the methods of the invention. Indeed, the vehicle equipped with means for obtaining the input data transmits this data to a storage means. The communication between the vehicle and the storage means can be fixed or radiofrequency, for example of the Bluetooth, Wi-Fi, GSM / GPRS type or any other frequency band or radiocommunication technology according to a national, regional or international standard. The storage means can also be in communication with an external system such as a drive over scanner, a database or any other system for obtaining quantities or storage of quantities. Communication between the storage medium and the external system is carried out independently by wire or by radio frequency communication. This storage means is in communication with a calculation means performing the calculation operations required by the methods of the invention. These calculation operations restore a result at the end of a process and are fed by input parameters which are input data or intermediate data stored on the storage means or results from a first calculation.

The system also has an analysis means which recovers input parameters of the result type conventionally which come from the storage means or from the calculation means and restores a decision on the level of wear or the prediction. end of life of the pneumatic enclosure. This decision can alternatively be transmitted or stored in the storage means by means of communication according to the actions to be taken depending on the nature of the decision such as, for example, wear at mid-height or wear at the limit. All of the communication arriving or departing from the analysis means is of a cord or radio frequency nature.

In a particular embodiment, the assembled assembly being equipped with a measuring device comprising a storage means and a means of transmission to the vehicle or at least one storage means, part of the input data comes from the assembled assembly.

In the case where the assembled assembly is equipped with a measurement sensor, making it possible to obtain, for example, the inflation pressure, the temperature of the fluid cavity of the assembled assembly, the load Z carried, the efforts at the wheel center, the mileage covered or the number of cycles carried out, equipped with means for storing measurement data and means of communication generally by radio frequency such as Bluetooth, Wi-Fi for communication to the vehicle or GSM / GPRS and low speed network for communication to an element external to the vehicle which could, for example, be the storage means, the assembled assembly becomes a secondary source or even the main source of input data. The assembled assembly, in this case, partially or totally replaces the vehicle for its functions within the system for implementing the methods of the invention.

Advantageously, the fourth transmission means comprises a means of transmission to the vehicle ensuring the communication of the at least one decision.

If the decision from the analysis means must be transmitted to a decision maker such as the driver of the vehicle due to the level of risk associated with the state of the tire, the system must be able to transmit the decision directly to the vehicle by means of any type of communication.

Preferably, the fourth means of transmission comprises a means of transmission to a third party such as the vehicle fleet manager ensuring the communication of the at least one decision.

If the decision from the analysis means is not urgent in relation to the security of the assembled assembly but requires a decision by a decision maker on future actions, such as, for example, operations preventive maintenance, the decision must be transferred as quickly as possible to this decision maker to organize maintenance or future operations. In other cases, the decision is transmitted to the storage means for traceability of the evolution of wear or the end-of-life prediction of the assembled assembly.

According to a very particular embodiment, part of the storage means and / or part of the calculation means and / or part of the analysis means are located on the vehicle or on the mounted assembly.

This is a special case where the vehicle is the physical host of the various elements of the implementation system. Thus, the vehicle has means of communication with external systems to have access to the various process input parameters. It also has a computer carrying out current operations to obtain the results of the methods and an analysis means to detect the critical states of the assembled assembly. The decisions are sent back to the driver or the manufacturer to either plan maintenance operations or adapt the use of the vehicle to the state of wear of the tire, for example.

Brief description of the drawings

The invention will be better understood on reading the description which follows. This application is given only by way of example and made with reference to the appended figures in which:

• The indexed figures 1 present curves for characterizing the longitudinal stiffness Kxx ^ref according to the usage parameters of a mounted assembly,

• Figure 2 presents characterizations of the longitudinal stiffness Kxx ^ref according to the thickness E of the tread of a mounted assembly and the effect of the ground;

FIG. 3 presents variations of the curves Fx (g%) of an assembly mounted on a vehicle according to two states of the tire on the same real ground,

• Figure 4 presents the end-of-life prediction of a tire evaluated using the method.

• Figure 5 is a block diagram of the methods of the invention. • Figure 6 is a diagram of the system for implementing the methods of the invention.

Detailed description of embodiments

The indexed figures of the to the present an illustration of the characterization curves of a mounted assembly constituted by a tire of dimension

235 / 35R19 of Michelin brand from the PilotSport 4S range mounted on a sheet metal machine wheel type 8.5J19 ET0. The assembled assembly thus constituted is inflated in nominal condition to 2.6 bars under a nominal load of 450 kg. The characterizations are carried out on a Flattrack type test bench fitted with an adhered floor 120 of the 3M brand. The assembled assembly undergoes a cycle of stresses consisting of braking and accelerations in a straight line after a 20 minute pre-rolling of the assembly assembled on a cycle of moderate stresses. This pre-rolling makes it possible to thermo mechanically put the assembled assembly in stabilized thermal condition.

The temperature and pressure measurements of the mounted assembly are carried out by means of a TMS placed on the inner rubber of the tire at the right of the crown so that the sensor is substantially in the plane. tire center. The load undergone by the mounted assembly is applied using the cylinder of the measurement bench where a dynamometric metric hub measures the vertical force Fz applied as well as the longitudinal components Fx and axial

Fy. The measurement is carried out at imposed force by controlling the vertical force Fz applied. A variation in torque around the axis of rotation of the assembled assembly is applied to the wheel center of the assembled assembly by means of the measuring bench. Fe applied torque is measured using the torque hub. In addition, the position of the axis of rotation of the assembled assembly relative to the running floor is measured as well as the speed of rotation of the wheel center of the assembled assembly through an encoder mounted between the stator and the rotor of the axis of rotation of the measuring bench. Finally, the scrolling of the ground is also controlled by the machine. In addition, a displacement sensor measures the speed of travel of the ground. The presence of the bonded coating makes it possible both to prevent the tire from slipping on the ground while respecting the optional condition of driving on smooth macro soil.

[Fig. the] presents for this assembled assembly, the experimental characterizations, represented by the points, obtained on a reference soil qualified as smooth macro for the aforementioned assembled assembly by varying the inflation pressure P of the assembled assembly between three pressures of inflation possible according to the ETRTO standard (English acronym for European Tire and Rim Technical O ...) for this assembly mounted for several controlled load and temperature conditions. The continuous curve is a transfer function model F (1005) of the independent influencing parameters type which minimizes the error between the experimental points and the mathematical model. A dependence of the second longitudinal stiffness Kxx ^{ref is} clearly observed on the inflation pressure P. The measurement points obtained under controlled metrological conditions make it possible to identify the various parameters of the transfer function F (1005) linked to the parameter of the inflation pressure.

[Fig.lb] and [Fig. the] represent the characterizations of the same assembled assembly carried out on the Flattrack type test bench by varying the temperature and the applied load respectively. The temperature variations in FIG. 1b correspond to variations in temperature of the mounted assembly that can conventionally be encountered according to diverse conditions of use. They are obtained by varying the regulated temperature of the cell hosting the measurement bench and by applying more or less sustained animation of the stress applied to the tire. For temperatures that are difficult to control on a measurement bench, the use of a digital simulation model of the assembled assembly was used. In a first phase, the digital model, in particular that of the tire, was validated on experimental measurements. In a second phase, numerical simulations were carried out for thermal stresses which are difficult to reproduce experimentally. For the digital model, the soil is a smooth adherent soil representative of the adhered soil on a measurement bench. The load variations for [Fig. the] are obtained by modifying the pilot load of the measurement bench while respecting the admissible loads by the assembly assembled according to the ETRTO standard.

Continuous curves are the mathematical model of the transfer function F (1005) identified for this set assembled by considering in the set of influential parameters, that the parameters are independent of each other. The registration of the mathematical model on the various experimental curves allows the unique identification of the various coefficients of the transfer function F (1005) of the assembly mounted on a reference soil of the macrolisse type.

Of course, the characterizations for the influential parameters of the first group G are carried out on at least three different levels of each influential parameter of the second group H such as the aging and the overall wear level of the tire and of the first group G other than the one we are trying to characterize.

Finally, having previously validated the digital model of the tire on experimental measurements of a particular mounted assembly, it is preferable to reuse this digital model of the tire in order to constitute a digital simulation campaign by modifying the other components of the assembled assembly, the thermomechanical stresses applied and the various states of the assembled assembly. Numerical simulations consume less time and resources than experimental campaigns after the validation phase of the numerical model of the tire.

[Fig.2] shows the evolution of the second longitudinal stiffness Kxx ^ref on a reference ground obtained for a mounted assembly comprising a tire of the Energy Saver type in dimension 195 / 65R15 mounted on an alloy wheel 6.5J15 ET23 . The measurements were made on a trader-type analytical trailer when driving on the test tracks, the macroroughness of which is controlled by profilometry. In this case, the variable parameter is the average thickness E of the tread, moreover controlling the various other influential stiffness parameters longitudinal such as the applied load, the inflation pressure and the temperature of the assembled assembly. The mobile measurement bench subjects the assembled assembly to various acceleration phases both in acceleration and in deceleration by applying a torque to the assembled assembly along the natural axis of rotation of the tire. The variation in the average thickness of the tread was obtained by automatic planing of the tires in the same tire preparation cycle. Thus, the aging of the various tires is similar. The altitude of the natural axis of rotation of the assembled assembly has been adapted so that the load applied to each assembled assembly is identical. The speed of the tire corresponds to the linear speed of the mobile test bench via the speed information of the mobile test bench retrieved from the CAN bus. A top wheel and a position means for measuring the height of the wheel center relative to the ground of the mounted assembly complete the equipment.

In general for the tires fitted to passenger vehicles and vans, the torque applied to the wheel center is of the order of 30 daN.m in order to ensure that the tire does not slip on the ground which is to say that the coefficient of slip of the tread material in use condition relative to the ground is not reached. Of course, this applied torque is to be adapted according to the category of tire to be measured.

The discrete measurements, represented by the points, correspond to the experimental characterizations of the longitudinal rigidity estimated during the tests on the reference ground of the test track. The curve in solid line corresponds to the second longitudinal rigidity evaluated using the transfer function F (1005) of the assembled assembly corrected by a passage function b (1004) associated with the reference soils. The other two curves, in dotted lines or continuous points, corresponding to the second longitudinal rigidities evaluated using the transfer function F (1005) of the assembled assembly, each corrected by a passage function b (1004) associated with the actual floors. 1 or 2. Here, the transfer function F (1005) used is also the product of power functions of the various independent parameters. Passage functions b (1004) make it possible to estimate the longitudinal stiffnesses on real ground by knowing only the transfer function F (1005) of the assembled assembly. The passage function b (1004), whatever the ground, is almost constant or depends on the thickness E of the tread for a given ground. The various soils are soils controlled in terms of roughness which make it possible for the same tire to obtain a variety of passage function b (1004) making it possible to take account of the nature of the soil.

Of course, it is possible to obtain an estimate of the influence of the aging D of the mounted assembly and in particular of the tire by preparing tires which have undergone differentiated aging by an identical method. For example, by accelerating aging by specific storage conditions, in an oven for example at various temperatures, or by carrying out rolling sessions of varying degrees of thermomechanical stress, differentiated aging is obtained between the tires. A planing of the various tires can also be carried out in this case in order to obtain the same thickness E of the tread before the characterization campaign for the identification of the transfer function F (1005).

[Fig. 3] presents the force curves Fx in the longitudinal direction of the assembled assembly as a function of the slip rate g% of an assembled assembly constituted by a tire of dimension 235 / 35ZR19 brand Michelin from the PilotSport 4S range mounted on an 8.5J19 ET20 type alloy wheel. This assembled assembly is mounted on the front axle of a FOCUS ST traction vehicle of the FORD brand.

The measurements were made on the same portion of road for two different tire states with the same conditions of use. The measurement points in gray represent a state of the tire having a thickness El and an aging DI close to the slightly worn and young state of the tire. The measurement points in black represent a second state of the tire corresponding to a thickness E2 and a level of aging D2 corresponding to a state close to the end of the life of the tire and to an aging equivalent to one year of average use. in a temperate country. Only the acceleration phases on the route up to engine torques not exceeding 35daN.m are shown here in order to consider that the tire does not slip on the road.

We estimate here, using the continuous curves defined as the linear regression line of the measurement points of each state of the tire, the first longitudinal stiffnesses (1009) on real ground of the two mounted assemblies. It is observed that the level of longitudinal stiffness on real ground is influenced by the state of the tire, the other parameters being considered as equivalent between the two states of the tire.

[Fig.4] represents the estimated monitoring of the overall wear of a tire compared to the evolution of a parameter U linked to the use of said tire. This parameter U can be, for example, the mileage traveled or the number of rotation cycles carried out by the tire. The estimation is made by obtaining the longitudinal rigidities (1009, 1010) made regularly during the use of the tire which are represented by the solid circles. Depending on the nature of the tread of the tire and an estimate of the soil macrugosity, a first passing function b (1004) is identified on a portion of the road where the parameters are measured regularly (1007, 1008) allowing the first longitudinal rigidity to be obtained on real ground (1009) and the second longitudinal rigidity on reference ground (1010). Thus, the method (1000) according to the invention makes it possible to estimate the variation in the average thickness of the tread during the use of the tire with respect to a characteristic thickness E0 (1002). We can then estimate a wear speed V (1013) by taking into account at least one variation of the average thickness DE of the tread between two obtention of the average thickness (1011) such as for example the new condition and a measurement during the use of the tire while knowing the variation AU (1012) of the parameter U between the two average thicknesses taken as reference. Knowledge of the end of life thickness E ^fm (1003) of the tread below which the security risks are highly accentuated identifies an end of life prediction according to the parameter U named U ^fm (1015) using the end of life prediction method (1100).

Of course, the prediction is based on an assumption concerning the passage function b (1004). If during the use of the tire, an E2 measurement of the average thickness of the tread is carried out, during a tire inspection by a professional of transport vehicles for example or the passage on a drive over scanner at the level of a motorway toll or a traffic light, a new evaluation of the passage function b (1004) of the road section can be carried out. This is reflected on the curve of FIG. 4 by a discontinuity which just illustrates the taking into account of the true measurement E2 of the average thickness of the tread. A new point, represented by a square in FIG. 4, illustrates this measurement point characterized by the thickness E2 of the tread. Then, the change in slope which may occur comes from an adjustment of the passage function b (1004) linked to a section of road. This adjustment is made by identifying a point of the passage function b (1004) linked to the overall wear level E2. Then the new curve obtained with a readjusted slope, reflecting the speed V of tire wear can be projected on the line defined by the end of life thickness E ^fm (1003) of the tread to estimate the end wear of life U ^fm (1015) of the tire. Here it is assumed that the estimation of the overall wear of the tire (1011) is carried out regularly on the same portion of road located by a geographic position. The change in soil can then come, for example, from the change in the portion of road taken as a reference for obtaining the first longitudinal rigidity (1009). The change in soil can also come from an adjustment of the passage function b (1004) during the use of the tire. Thus, in the new state, a flat-rate function is assigned to the passage function b (1004) as the identity function by ignorance of the nature of the soil where the measurement cycle is carried out. During the use of the tire, by using a method for characterizing the passage function b (1004) such as for example a true measurement of the average thickness E2 of the strip of rolling allowing to identify a passage function b (1004) more representative of the nature of the soil.

[Fig.5] shows a block diagram integrating the method (1000) for estimating the overall wear and the method (1100) for predicting the end of life of a tire in running condition on a vehicle.

Step 1001 is the identification of the assembled assembly and more particularly of the tire. This step can be done by assigning the identifier of the components of the mounted assembly associated with the vehicle to a database.

The identification 1001 firstly makes it possible to define a characteristic thickness E0, corresponding to step 1002, such as for example the thickness in new condition and the end of life thickness E ^fm of the tire, corresponding in step 1003. Then, the identification 1001 of the mounted assembly also makes it possible to know the rigidity of the tread of the tire, which makes it possible to estimate one or a few passage functions b (1004) each associated with a portion of the road characterized by macroroughness among a possible plurality of crossing functions. Failing this, the user chooses a passage function b (1004) from the list of potential passage functions b which is representative of the median nature of the portions of road that the vehicle will encounter. The choice of the passage function b corresponds to step 1004. Finally, the identification 1001 also makes it possible to choose the transfer function F of the mounted assembly corresponding to step 1005. This transfer function F is essential for the method of estimating overall wear.

Then, if necessary, the user informs the state of aging of the tire, corresponding to step 1006. This passes through the identification (1001) of the tire in order to know the history of use. tire. This history can be filled in by querying a database. This database can be external to the assembled assembly, present on the vehicle or on a server. If the tire DI (1006) aging state only concerns the age of the product or the total number of cycles performed or kilometers traveled, the information may be present on the assembly mounted through an electronic device of TMS or TPMS type. This step 1006 necessarily takes place during a state cycle comprising the measurement cycle allowing the evaluation of the average thickness of the tire.

The next steps 1007 and 1008 are carried out during a measurement cycle. The first step 1007 consists in obtaining, when traveling in a straight line on a dry road comprising acceleration and deceleration phases, the forces Fx measured at the wheel center of the assembled assembly and the associated slip rate g%. In the absence of direct forces Fx at the wheel center, access to parameters Q1 of the vehicle allowing an estimation of the forces Fx at the wheel center, for example, the torque applied to the wheel center around the natural axis of rotation of the assembly. mounted during acceleration or deceleration phases. Step 1008 corresponds to obtaining the usage parameters of the assembled assembly such as the inflation pressure PI, the temperature T1 of the assembled assembly and the load ZI applied or the parameters Q2 of the vehicle enabling the charge ZI to be obtained. . These parameters Q2 can for example be the static mass of the vehicle, the filling level of the fuel tank and the indication of the number of seat belts fastened. This step 1008 must be carried out just before, during or after the straight line rolling carried out in step 1007.

Step 1009 follows chronologically Step 1007 although it can be done between two measurement cycles. From the forces Fx measured or evaluated and the slip rates g% associated during driving on the dry road portion, a point cloud associated with the doublet of values is drawn (Fx, g%). It is retained from this cloud of points that all of the points for which the tire does not slip on the road portion. Finally, the linear regression line of the set of points is identified. The slope of this regression line corresponds to the estimate of the first longitudinal stiffness Kxx ^reel on real ground corresponding to the portion of dry road. Step 1010 follows chronologically step 1008 coupled to steps 1002 and 1005. Thus, from the transfer function F (1005) chosen thanks to the identification (1001) of the assembled assembly, it is estimated a second longitudinal stiffness on reference soil Kxx ^ref by supplying the transfer function F (1005) with the measured usage parameters PI, TI and ZI in step 1008 and the characteristic thickness E0 chosen in step 1002. Depending on the sensitivity of the characteristics of the assembled assembly to aging, this step 1010 can also be coupled to step 1006 in which an evaluation of the aging DI of the assembled assembly is carried out.

The next step 1011 corresponds to the evaluation of the average thickness of the tread and consequently of the overall wear of the tire by comparing this average thickness evaluated with the specific thicknesses of the tire such that E ^fm and E0. For this, a relation linking the results of steps 1004, 1007 and 1008 is applied, the result of which is the average thickness E associated with the state cycle of the tire. In the case where the second longitudinal rigidity on reference ground Kxx ^ref (1010) is defined using a transfer function F (1005) which is the product of power functions of independent influent parameters as claimed in the claim, the thickness E can then be isolated from this transfer function F (1005) as being the product of the constant E _ref by the root alpha of the ratio between the first longitudinal rigidity on real soil (1009) on the product of the function of passage b (1004) by the second longitudinal rigidity on reference soil (1010). We will assume here that the passage function b (1004) is constant with the average thickness of the tread. In the case of influencing parameters dependent on each other, the identification relationship of the average thickness E is more complex.

The next step 1012 consists in obtaining the variation AU of a parameter U linked to the use of the tire between two obtaining the average thickness of the tread. The parameter U can be for example, the number of cycles of rotation around the natural axis of rotation or the number of kilometers traveled by the tire tread or time of use. The two obtaining (El, E2) of the average thickness of the tread may for example be two evaluations carried out by the method corresponding to two states of wear of the tire or an evaluation of the average thickness of the tread combined with the new condition of the tire or a measurement of the average thickness of the tire by an external measuring means.

The next step 1013 is the evaluation of the speed V of wear of the tire and more precisely of the tread at a point of obtaining the average thickness of the tread of the tire. . For this, it is necessary to have both the variation AU of the parameter U linked to the use of the tire obtained in the previous step and the variation of the corresponding average thickness DE. The variation DE is the difference between the two obtaining (El, E2) having served as reference points for the variation AU carried out in the previous step. The ratio of the variation in the average thickness DE to the variation in the parameter linked to the use of the tire Du defines the speed V of wear of the average thickness of the tread according to the parameter U.

Of course, the variation AU of the parameter U linked to the use of the tire can also result from the difference in the obtaining (Ul, U2) of the parameter U carried out in step 1014.

Finally, the final step 1015 consists in evaluating the end of life prediction U ^end according to the parameter U linked to the use of the tire. This is obtained by combining the results of steps 1003, 1011, 1013 and 1014.

[Fig.6] is a block diagram of the system for implementing methods for estimating the level of overall wear and predicting the end of life of a tire. The block diagram comprises structural elements represented by bubbles and means of transmission between the structural elements represented by a line between the structural elements. The line may include at its end a solid circle representing a point of arrival of the means of transmission or a solid diamond representing a starting point for the means of transmission. However, the direction of communication indicated can also be bilateral, for example if the process includes a phase of interrogation from one structural element to another structural element. Finally, the synoptic also includes the data contained and exchanged between the various structural elements in the form of rectangles.

The input data are present at the level of the vehicle 2001. These can also be present at least partially at the level of the assembled assembly 2006 comprising the tire which is the center of interest of the methods, objects of this invention. These input data pass to a storage means 2002 by means of transmission 2101. In the case where a part of the input data comes from the assembled assembly 2006, these are directly or through of the vehicle 2001 transmitted to the storage means 2002. The transmission means coming from the assembled assembly, denoted 2105 are represented by black dots.

The intermediate data contained in the storage means 2002 come in part from the input data from the vehicle 2001.

However, they can also come from an external system 2005 via transmission means 2106. This intermediate data coming from an external system can be, for example, the transfer function L associated with the mounted assembly or the passage function b making the link between the rigidity of the tire tread and the nature of the road section.

Then, the system includes a calculation means 2003 making it possible to obtain the various results by operations between the intermediate data. Therefore, a transmission means 2102 allows the communication of intermediate data to the calculation means 2003 to generate results.

These results can then pass through means of transmission.

2103 in dotted lines towards the analysis means 2004 either directly or via the storage means 2002. The analysis means 2004 then delivers a decision which will be, via transmission means 2107 in gray lines dotted with dots and dotted lines, transmitted directly to the vehicle 2001 or to a third party 2007 or stored at the level of the storage means 2002 according to the urgency of the decision.

This decision can be information on the state of wear E of the tire with respect to the thickness E ^fm of the end of life of the tire. The decision can also be according to the end of life prediction U ^fm of the tire, actions for changing the tire to be planned or to be carried out quickly. In the first case, the information will be sent to a fleet manager to organize the planning. In the second case, the decision goes back to the vehicle so that, on the one hand, the driver can adapt the conditions of use of the tire to its state of wear and that he anticipates changing the tire as soon as possible.

Claims

1. Method (1000) for estimating the overall level of wear of a tire of an assembly mounted in running condition on a vehicle, the tire having a crown which is extended by two sidewalls ending in two beads, of revolution around a natural axis of rotation, the apex comprising a tread located radially outside the tire with respect to the natural axis of rotation, said tread having an average thickness E (1011), the assembled assembly comprising components, including a wheel and the tire, delimiting an internal cavity, comprising the following steps:

Obtain a transfer function F (1005) of the assembly mounted between a longitudinal stiffness K _xx ^ref on a reference soil and influencing factors, as being the product of a first function F1 having as influencing factors at least the pressure of inflation P, the temperature T and the load Z undergone, by a second bijective function F2 having at least as factor influencing the thickness E of the tread;

Obtain a passage function b (1003) of the assembled assembly defined for a portion of road as being the ratio of the longitudinal rigidities Kcc of the assembled assembly with iso influencing factors, of which that in the numerator is evaluated on a soil equivalent to the portion of road and that in the denominator is evaluated on a reference soil;

On the same measurement cycle:

Determine at least one effort Fx undergone by the assembled assembly and at least one slip rate g% at the wheel center of the assembled assembly, or obtain parameters Q1 of the vehicle allowing their said determinations (1007), during a taxiing in a straight line of the vehicle comprising variations in acceleration on said portion of road, the latter being dry;

Determine a load Zl, or obtain parameters Q2 of the vehicle allowing said determination, undergone by the assembly mounted in running condition (1008); Determine a temperature Tl of the assembly assembled in running condition (1008)

Determine an inflation pressure PI of the internal cavity of the assembly assembled in running condition (1008), and

characterized in that it comprises obtaining a first longitudinal stiffness Kxx ^reel (1009) of the assembly mounted on real ground using a first relationship linking the forces Fx, the slip rates g% or the parameters Ql, in that it comprises obtaining a second longitudinal rigidity on the reference ground Kxx ^ref (1010) evaluated using the transfer function F (1005) supplied by at least the influencing factors Tl, PI, ZI or the parameters Q2 (1008) and at least one characteristic thickness E0 (1002) of the tread, in that it comprises obtaining a scalar bi defined using the function of passage b fed by at least the influencing factors Tl, PI, ZI and in that the thickness E (1011) of the tread is determined by a first relation linking the scalar bi, the first longitudinal stiffness Kxx ^reel (1009 ) and the second longitudinal stiffness Kxx ^ref (1010) as follows:

2. Method (1000) for estimating the overall wear level of a tire of a mounted assembly according to claim 1 in which, the transfer function F (1005) of the mounted assembly depending on the aging D of at least one of the components of the assembled assembly, the method comprises obtaining the aging DI (1006) of at least one component of the assembled assembly in a first state cycle of the assembled assembly comprising the measurement cycle , and obtaining the second longitudinal stiffness Kxx ^ref (1010) is carried out by using the aging DI (1006) of at least one component of the assembled assembly.

3. Method (1000) for estimating the overall wear level of a tire of a mounted assembly according to one of the preceding claims, in which obtaining the transfer function F (1005) of the mounted assembly is carried out through a characterization campaign included in the group comprising numerical simulation and experimental measurements.

4. Method (1000) for estimating the overall wear level of a pneumatic casing of an assembled assembly according to one of the preceding claims, in which the transfer function F (1005) is obtained on the smooth macro soil.

5. Method (1000) for estimating the overall wear level of a tire of a mounted assembly according to one of the preceding claims, in which the transfer function F (1005) is obtained by using a mathematical model of the type:

Or,

G ^J o and E _ref are constants:

(¾, and a are reals;

G ¹ are influencing factors;

E is the thickness of the tread.

6. Method (1000) for estimating the overall wear level of a tire of a mounted assembly according to any one of claims 4 to 5 in which, obtaining the passage function b (1004) comprises the following steps:

- Carry out a set of measurement cycles associated with various road sections, the road sections being dry, in the same state cycle of the assembled set, Obtain for each measurement cycle the first longitudinal stiffness kxx on real ground and the second longitudinal stiffness k'xx ^ref on reference ground,

Evaluate for each measurement cycle a difference X between the first and the second longitudinal stiffness.

Define a target measurement cycle among all the measurement cycles by identifying the one with the smallest deviation X;

7. Method (1000) for estimating the overall wear level of a tire of a mounted assembly according to any one of claims 1 to 5 in which obtaining the passage function b (1004) comprises the following steps :

Obtain an average thickness E2 of the tread;

Perform a measurement cycle associated with a road section, said road section being dry, in the same state cycle of the assembled assembly; Obtain the first longitudinal stiffness kxx on real ground;

Obtain a third longitudinal stiffness k ”xx ^ref on reference soil evaluated using the transfer function F supplied by influencing factors including the influencing factors obtained during the measurement cycle and at least the thickness E2 of the strip of rolling ;

Obtain a coefficient l as the ratio of the first longitudinal rigidity kxx on real soil to the third longitudinal rigidity k ”xx ^ref on reference soil;

Determine the passage function b associated with the portion of road passing through the point (l, Pi, Zi, Ti) associated with the measurement cycle.

8. Method for estimating (1000) the overall wear level of a tire of a mounted assembly according to one of claims 1 to 5 in which, obtaining the passage function b (1004) comprises the following steps : Obtain a second passage function b2 of the mounted assembly defined for a second portion of road;

Obtain for the soil of the second portion of the road a vector M2 characterizing the macrorugosity of the soil relative to the reference soil; Obtain for the soil of the road portion a vector M characterizing the macrorugosity of the soil relative to the reference soil;

Determine the passage function b of the mounted assembly defined for the road portion e by a relation linking the passage function b2 and the relative position of the vector M2 with respect to the vector M.

9. Method (1000) for estimating the overall wear level of a tire of an assembled assembly according to one of claims 1 to 8 comprising the additional steps:

Determine a variation AU (1012) between at least two obtaining the thickness E of the tread of at least one parameter U linked to the use of the tire included in the group comprising rotation cycles carried out, kilometers traveled, time, tire usage time;

Determine at least one speed V (1013) of overall tire wear defined by the ratio between a variation DE of the thickness E between the at least two thicknesses E (1011) of the tread and the variation AU (1012) of at least one parameter U linked to the use of the tire.

10. Method (1100) for predicting the end of life of a tire having a tread located radially outwardly relative to a natural axis of rotation of the tire, having an average thickness E, a characteristic thickness E0 (1002) and a end of life thickness E ^fm (1005), comprising the following stages:

Determine at least one thickness El (1011) of the tread of a tire during at least one first state cycle of the tire of a first mounted assembly comprising said tire by using the method (1000) of estimating the overall wear of a tire according to one of claims 1 to 8;

Determine a speed VI (1013) of tire wear associated with the at least one thickness El using the method (1000) of estimating the overall wear of a tire according to claim 9;

Determine a value U1 (1014) of the parameter U associated with the at least one thickness El (1011);

Determine the end-of-life prediction of the tire using a value U ^fm (1015) of the at least one parameter U linked to G use of the tire defined by a second function linking the wear speed VI (1013), the at least one thickness El (1011) associated with a value U1 (1014) of the parameter U and the end of life thickness E ^fm (1005).

11. System (2000) for implementing the method (1000) for estimating the overall wear level of a tire according to one of claims 1 to 9 and / or the method (1100) for predicting end of life of a tire according to claim 10 comprising:

- a vehicle (2001) equipped with at least one mounted assembly (2006) comprising said tire that can be put into driving condition; at least one storage medium (2002),

at least one means of calculation (2003),

at least one means of analysis (2004),

at least one first transmission means (2101) between the vehicle (2001) and the at least one storage means (2002),

at least one second means of transmission (2102) between the at least one means of storage (2002) and the at least one means of calculation (2003), at least one third means of transmission (2103) between the at least one means of 'analysis (2004) and the at least one means of storage (2002) or the at least one means of calculation (2003), input data from the vehicle (2001),

intermediate data stored in the at least one storage means (2002) which can be transmitted by at least one external system (2005),

- at least one output result from at least one calculation means

(2003),

at least one decision from at least one analysis means (2004), in which the input data are included in the group comprising the load Zl, the temperature Tl, the pressure PI, the force FX, the rate of slip g%, the parameters Q1 and Q2, the at least one parameter U linked to the use of the tire and the variations AU of the at least one parameter U, in which the intermediate data are included in the group comprising the thickness E2, the aging DI of at least one component of the mounted assembly, the characteristic thickness E0 and the end of life thickness E ^fm of the tread of said tire, the transfer function F of the mounted assembly, the function of passage b of the assembled assembly associated with the road portion, the vector M characterizing the macroroughness of the soil of the road portion relative to a reference soil, in which the at least one output result is included in the group comprising the thickness E of the tread of said tire, the overall wear speed V of said tire, the end of life prediction U ^fm of the tire associated with the parameter U, the first longitudinal stiffness kxx ^reel , the second longitudinal stiffness k'xx ^ref , the third longitudinal stiffness k ”xx ^ref and in which the at least one decision expressing the state of wear of the tire is transmitted and / or stored in the at least one storage means (2002), using at least one fourth transmission means ( 2104).

12. System (2000) for implementing the method (1000) for estimating the overall wear of the tire and / or the method (1100) for predicting the end of life of a tire according to claim 11 in which, the assembled assembly (2006) being equipped with a measuring device comprising a storage means and a means of transmission (2105) to the vehicle (2001) or the at least one storage means (2002), part of the input data comes from the assembled assembly (2006).

13. System (2000) for implementing the method (1000) for estimating the overall wear of the tire and / or the method (1100) for predicting the end of life of a tire according to one claims 11 to 12 wherein, the at least one fourth transmission means (2104) comprises a transmission means to the vehicle (2001) ensuring the communication of the at least one decision.

14. System (2000) for implementing the method (1000) for estimating the overall wear of the tire and / or the method (1100) for predicting the end of life of a tire according to one Claims 11 to 12, in which the at least one fourth transmission means (2104) comprises a transmission means to a third party (2007) such as the vehicle fleet manager ensuring the communication of the at least one decision.

15. System (2000) for implementing the method (1000) for estimating the overall wear of the tire and / or the method (1100) for predicting the end of life of a tire according to one Claims 11 and 14 in which part of the at least one storage means (2002) and / or part of the at least one calculation means (2003) and / or part of the at least one analysis means (2004) are located on the vehicle (2001) or on the assembled assembly (2006).