Wheel equipped with a capacitive radial-deflection sensor, vehicle equipped with such a wheel, and method for capacitively measuring the load on a wheel and a vehicle

Abstract

The invention relates to a wheel (300) comprising a rim (202) and a tyre (304), characterized in that it further comprises at least one capacitive sensor (100) for measuring a radial deflection of said wheel, the capacitive sensor (100) comprising: - at least one capacitive-measurement electrode positioned in the wheel (300) facing the rim (302) or facing the tyre (306); - at least one electrode, referred to as an earthing electrode, for electrically earthing at least one measurement electrode; - measurement electronics for:  polarizing said electrodes with an alternating working electrical potential; and measuring an electrical signal (Vs,Vu) relating to the capacitance observed by said measurement electrode and indicative of the radial deflection of said wheel (300). It also relates to a vehicle equipped with such a wheel, to a method for capacitively measuring a load applied to a wheel and to a method for capacitively measuring a load applied to a vehicle.

Description

DESCRIPTION Title: Wheel equipped with a capacitive radial deflection sensor, vehicle equipped with such a wheel, and method for capacitively measuring a load of a wheel and a vehicle.

[0001] The present invention relates to a wheel equipped with a capacitive sensor for measuring a radial deflection of said wheel, in particular when subjected to a load, in particular in the vertical direction. It also relates to a vehicle equipped with such a wheel. The invention also relates to a method for capacitively measuring a load applied to a wheel and a method for capacitively measuring a load applied to a vehicle.

[0002] The field of the invention is the field of measuring a radial deflection of a wheel, in particular to determine the load applied to the wheel. State of the art

[0003] There are different solutions for determining a load applied to a wheel.

[0004] For example, there are systems based on measuring the wheel's footprint. These systems allow for efficient and accurate measurement of the load applied to a vehicle's wheel, whether the vehicle is stationary or moving.

[0005] There are also systems based on measuring radial deflection, for example using ultrasound or laser beams.

[0006] However, most systems are quite complex, bulky, and expensive to implement. In addition, most systems require a fairly lengthy calibration for each wheel type. Furthermore, these systems rely on a change in the wheel's internal cavity, or a change in the wheel's footprint, which is difficult to measure.

[0007] An aim of the present invention is to remedy at least one of the aforementioned drawbacks.

[0008] Another aim of the invention is to propose a solution making it possible to measure a load applied to a wheel in a simpler manner.

[0009] Another aim of the invention is to propose a solution making it possible to measure a load applied to a wheel that is less heavy to implement.

[0010] Another aim of the invention is to propose a solution for measuring a load applied to a wheel that is less expensive to implement. Statement of the invention

[0011] The invention proposes to achieve at least one of the aforementioned aims by a wheel comprising a rim and a tire characterized in that it further comprises at least one capacitive sensor of a radial deflection of said wheel, said capacitive sensor comprising: - at least one capacitive measuring electrode arranged in said wheel opposite said rim or said tire; - at least one electrode, called a guard electrode, for electrically guarding said at least one measuring electrode; and - measuring electronics for: ■ polarize said electrodes at an alternating electric potential, called working potential, different from a potential of said wheel, at a frequency, called working, and ■ measure an electrical signal, called the measurement signal, relating to the capacitance seen by said measuring electrode and representative of the radial deflection of said wheel.

[0012] Thus, the invention proposes a solution for detecting the radial deflection of a wheel. The inventors discovered that the radial deflection of a wheel is directly related to the load applied to said wheel. However, measuring the radial deflection of a wheel is simpler to implement compared, for example, to measuring the footprint of a wheel or measuring the deformation of the inner cavity of the wheel.

[0013] Furthermore, the invention proposes to detect the radial deflection of the wheel using at least one capacitive sensor comprising at least one capacitive measuring electrode arranged in the wheel, and in particular in the internal cavity of the wheel, which is simpler, less expensive, and less cumbersome to implement compared to current techniques.

[0014] Furthermore, the solution proposed by the invention is less cumbersome to implement because it uses capacitive electrodes whose size is very reduced compared, for example, to sound sensors.

[0015] Finally, the solution proposed by the invention can be implemented both for existing wheels, or new wheels currently being produced. For example, the capacitive electrodes can be integrated into the wheel, respectively into the tire or even into the rim, at the time of manufacturing the wheel, respectively the tire or the rim.

[0016] In the present application, "radial deflection" of the wheel means a displacement of the rim relative to the ground, in the vertical direction, due to a load applied to said wheel and which results in crushing of the tire.

[0017] The guard electrode protects the measuring electrode from stray capacitive couplings, or from disturbances coming from below the measuring electrodes, and thus increases the accuracy and measuring range of the measuring electrodes. Since the guard electrode is polarized at the same potential as the measuring electrodes, it is electrically invisible at the working potential frequency.

[0018] Of course, the guard electrode is electrically insulated from the measuring electrode, for example by a dielectric layer arranged between the measuring electrode and the guard electrode. Such a dielectric layer can be a PCB board, or a layer of dielectric varnish, a layer of dielectric paint, etc.

[0019] For example, the measuring electrode may be disposed on a first face of an electronic card and the guard electrode may be disposed on the opposite face of said electronic card.

[0020] According to embodiments, the guard electrode can be arranged on the rim, respectively the tire, when the measuring electrode is arranged on the side of said rim, respectively of said tire, while being electrically insulated from said rim or said tire.

[0021] According to embodiments, when the measuring electrode is arranged on the rim side, the guard electrode can be formed by said rim, the latter then being polarized at the working potential.

[0022] According to non-limiting embodiments, at least one capacitive sensor may comprise a coplanar measuring electrode and a guard electrode.

[0023] Such an architecture makes it possible to further reduce the size of the capacitive sensor.

[0024] In addition, the presence of a guard electrode in the same plane as the measuring electrode makes it possible to better guard the measuring electrode, in particular with regard to disturbances coming from the sides of the measuring electrode, which makes it possible to improve the measurement of a quantity relating to the radial detection of the wheel.

[0025] Alternatively, or in addition, at least one capacitive sensor may comprise a guard electrode disposed below a measuring electrode.

[0026] The presence of such a guard electrode under a measuring electrode makes it possible to better guard the measuring electrode, in particular with regard to disturbances coming from below the measuring electrode, which makes it possible to improve the measurement of a quantity relating to the radial detection of the wheel.

[0027] Alternatively, or in addition, at least one capacitive sensor may comprise a guard electrode and a measuring electrode: - interlaced or comb-shaped, and / or - concentric

[0028] Such an architecture of the measuring and guard electrodes makes it possible to further reduce external disturbances while improving the size of the capacitive electrodes and therefore of the capacitive sensor.

[0029] According to non-limiting embodiments, for at least one capacitive sensor, the measuring electrode, respectively the guard electrode, can be arranged integral with the tire, in particular in a central zone of said tire in the direction of the width of said tire, and even more particularly in a central part of the tread of said tire. In this case, the measuring electrode is sensitive to the position of the rim of the wheel relative to the tire, during the radial deflection of said wheel, and therefore modify the total capacitance seen by the measuring capacitance.

[0030] In this embodiment, the capacitive electrode(s) may be arranged: - in the thickness of the tire, or - on an internal face of said tire, or - on a support itself arranged on said, or secured to said, tire and in particular on an internal face of said tire.

[0031] According to non-limiting embodiments, for at least one capacitive sensor, the measuring electrode, respectively the guard electrode, can be arranged integral with the rim. In this case, the measuring electrode is sensitive to the position of a metal part of the tire, or of a metal target integral with the tire, during the radial deflection of said tire.

[0032] In this case, the measuring electrode, or the guard electrode, can be arranged on the rim, or on a support itself arranged on, or secured to, said rim.

[0033] At least one capacitive sensor may comprise at least one electrode, called a reference electrode, arranged so as not to be sensitive to a radial deflection of said wheel.

[0034] Such a reference electrode makes it possible to measure the effects of temperature and pressure in the wheel and to correct the capacitive measurement made with the measuring electrodes for any drifts caused by a variation in temperature or pressure.

[0035] For example, the reference electrode may be arranged below the guard electrode, if applicable.

[0036] According to another example, the reference electrode may be oriented in a direction other than the radial direction, for example in a direction perpendicular to the radial direction.

[0037] According to embodiments, at least one capacitive sensor may comprise an electrode, called an interaction electrode: - polarized to the wheel potential, and - placed firmly on the tire, opposite the measuring electrode placed on the rim.

[0038] Such an interaction electrode thus makes it possible to form a conductive surface for measuring deflection, when the tire does not have a metal component or carcass. The interaction electrode has the advantage of increasing the coupling with the measuring electrode and increasing the measurement sensitivity. In addition, it makes it possible to strengthen the propagation of the sensor's field lines towards the bottom of the tire.

[0039] When the tire has a carcass comprising at least one metal part, it is not necessary, but is not prohibited, to use such an interaction electrode. Such a carcass may comprise a metal sheet or a metal belt, etc. Indeed, in this case, the metal part of the tire carcass disrupts the capacitive coupling between the measuring electrodes, in a manner proportional to the radial deflection of the tire.

[0040] Of course, when the measuring electrode is arranged on the side of the tire opposite the metal rim, it is not necessary, but is not prohibited, to use such an interaction electrode. Indeed, in this case, the electrically conductive rim is detected by the measuring electrode during the radial deflection of the wheel, in a manner proportional to the radial deflection of the tire.

[0041] According to an advantageous characteristic, at least one capacitive sensor can comprise a first module for calculating a deflection value, as a function of the measurement signal.

[0042] Such a first module may comprise a hardware module formed by at least one digital component, such as a processor or an electronic chip or a calculator, or at least one analog component, or by a combination of at least one digital component and at least one analog component.

[0043] Alternatively, or in addition, such a first module may comprise a software module.

[0044] The calculation of the value of the radial deflection of the wheel can be carried out as a function of the value of the measurement signal and at least one predetermined deflection calculation model relating the value of the measurement signal to a value of the deflection. The predetermined deflection calculation model can comprise: - a predetermined mathematical relationship, or - a table of predetermined values, for example during a calibration phase, storing for different values ​​of the measurement signal the corresponding deflection values ​​measured during said calibration phase.

[0045] In the case where no sensor is aligned with the normal to the road surface / contact footprint, it is possible to estimate the deflection by reconstructing the radial displacement profile measured by the sensors distributed on the rim. From the radial displacement profile and a representative function of this displacement or by interpolation, the deflection value can be estimated.

[0046] According to an advantageous characteristic, at least one capacitive sensor can comprise a second module for calculating a load value applied to the wheel.

[0047] The load value can be deduced from: - the value of the measurement signal, or - a radial deflection value itself previously determined as a function of the measurement signal.

[0048] Such a second computing module may comprise a hardware module formed by at least one digital component, such as a processor or an electronic chip or even a calculator, or at least one component analog, or by a combination of at least one digital component and at least one analog component.

[0049] Alternatively, or in addition, the second module may include a software module.

[0050] The calculation of the load value may be performed based on at least one predetermined load calculation model. The predetermined load calculation model may include: - a predetermined mathematical relationship, or - a table of predetermined values, for example during a calibration phase.

[0051] Advantageously, the wheel according to the invention can comprise at least one electrical source delivering the working potential to at least one capacitive sensor.

[0052] Such an electrical source can be an alternating voltage source providing the working potential.

[0053] The alternating working potential can be a sinusoidal, square, etc. potential.

[0054] According to embodiments, the wheel according to the invention may comprise several capacitive sensors. These sensors may preferably, but in no way limitatively, be distributed around the axial direction of said wheel.

[0055] Capacitive sensors can be paired together.

[0056] The sensors forming a pair may be arranged around the axial direction at opposite, or symmetrical, locations relative to said axial direction. Thus, it is possible to perform a deflection measurement by one of the sensors of a pair of sensors and to correct the measured value using the other of the sensors of the pair of sensors, for example to correct errors or drifts due to variations in temperature, pressure or any other variation affecting the capacitive measurement.

[0057] Alternatively, or in addition, these sensors forming a pair may be arranged around the axial direction at locations separated by an angle of 90° around the axial direction. Thus, it is possible to carry out a deflection measurement by one of the sensors of a pair of sensors and to correct the measured value using the other of the sensors of the pair of sensors, for example to correct errors or drifts due to variations in temperature, pressure or any other variation affecting the capacitive measurement.

[0058] According to another aspect of the same invention, there is provided a vehicle equipped with at least one wheel according to the invention.

[0059] Such a vehicle may be a land vehicle such as a car, bus, coach, truck, heavy goods vehicle, trailer, etc.

[0060] Such a vehicle may be a flying vehicle such as an airplane or helicopter equipped with wheels used for takeoff or landing.

[0061] According to embodiments, the vehicle according to the invention may comprise: - several wheels according to the invention, and - a module for calculating the weight of said vehicle.

[0062] Such a calculation module may comprise a hardware module formed by at least one digital component, such as a processor or an electronic chip or a calculator, or at least one analog component, or by a combination of at least one digital component and at least one analog component.

[0063] Alternatively, or in addition, the weight calculation module may include a software module.

[0064] The vehicle weight calculation is performed based on signals received from each wheel and a predetermined weight calculation model relating these signals to a weight value. The predetermined weight calculation model may include a predetermined mathematical relationship.

[0065] The signal received from each wheel can be a capacitive measurement signal, a deflection value or a load value.

[0066] According to another aspect of the same invention, there is provided a method for determining a load applied to a wheel, in particular to a wheel according to the invention, comprising at least one iteration of a measurement phase comprising the following steps: - measurement of a measurement signal relating to a radial deflection of said wheel by at least one capacitive sensor arranged in said wheel, and - calculation of a value of a load applied to said wheel, as a function of said measurement signal and a predetermined load calculation model.

[0067] The predetermined model may be the second predetermined model described above.

[0068] The calculation of the value of the load applied to the wheel can be determined using the measurement signal, or a radial deflection value previously calculated from said measurement signal.

[0069] The load calculation model can be determined during a calibration phase prior to the first measurement phase.

[0070] According to examples of implementation, the load calculation model may include: - a predetermined mathematical relationship, or - a table of predetermined values; linking a measurement signal value, respectively a radial deflection value, to a load value.

[0071] According to another aspect of the same invention, there is provided a method for determining a weight of a vehicle comprising several wheels, said method comprising at least one iteration of a weighing phase comprising the following steps: - measurement of load values ​​applied to several wheels of said vehicle by the method according to the invention; and - calculating a weight of said vehicle from said load values ​​and a predetermined weight calculation model

[0072] The predetermined weight calculation model may be the third predetermined model described above.

[0073] The calculation model can be predetermined during a calibration phase prior to the first weighing phase.

[0074] According to exemplary embodiments, the predetermined weight calculation model may comprise: - a predetermined mathematical relationship, or - a table of predetermined values; linking wheel load values ​​of a vehicle to a weight value of said vehicle. Description of figures and embodiments

[0075] Other advantages and characteristics will appear on examining the detailed description of non-limiting embodiments, and the attached drawings in which: - FIGURE 1 is a schematic representation of an exemplary embodiment of a capacitive sensor which can equip a wheel according to the invention; - FIGURES 2a-2g are schematic representations of non-limiting exemplary embodiments of electrode arrangements that can be implemented in the present invention; - FIGURES 3-5 are schematic representations of non-limiting exemplary embodiments of a wheel according to the invention; - FIGURE 6 is a schematic representation of a non-limiting exemplary embodiment of a vehicle according to the invention; - FIGURE 7 is a schematic representation of a non-limiting exemplary embodiment of a method according to the invention for measuring the load applied to a wheel; and - FIGURE 8 is a schematic representation of a non-limiting exemplary embodiment of a method according to the invention for measuring the weight of a vehicle.

[0076] It is understood that the embodiments which will be described below are in no way limiting. In particular, we can imagine variants of the invention comprising only a selection of features described below isolated from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art. This selection includes at least one preferably functional feature without structural details, or with only a part of the structural details if it is this part which is only sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art.

[0077] In particular, all the variants and embodiments described can be combined with each other if nothing prevents this combination from a technical point of view for a person skilled in the art.

[0078] In the figures and in the rest of the description, the elements common to several figures retain the same reference.

[0079] FIGURE 1 is a schematic representation of a non-limiting exemplary embodiment of a capacitive sensor that can be fitted to a wheel according to the invention.

[0080] The capacitive sensor 100 comprises a measuring electrode 102. The capacitance C seen by the measuring electrode 102 changes in the presence of an object O, as well as depending on the distance between the object O and the measuring electrode 102. Thus, the measurement of the electrical signal relating to the capacitance C seen by the measuring electrode 102 makes it possible to characterize the distance between the measuring electrode 102 and the object O.

[0081] Of course, the number of measuring electrodes in the capacitive sensor 100 is not limited to 1.

[0082] The capacitive sensor 100 may comprise a guard electrode 104, disposed under the measuring electrode 102, and provided to electrically guard the measuring electrode 102 against disturbances coming from the direction opposite to the measuring direction.

[0083] The measuring electrode 102 and the guard electrode 104 are intended to be placed at the same alternating potential, called the working potential, and noted T in the following, different from a ground potential, noted M.

[0084] The capacitive sensor 100 further comprises measurement electronics 110 for measuring a measurement signal representative of the coupling between the measurement electrode 102 and the object O, and therefore of the distance between the measurement electrode 102 and the object O. In the example shown, in a non-limiting manner, the measurement electronics 110 comprise a current or charge amplifier, comprising an operational amplifier (AO) 112 and a feedback capacitor 114 looping the output of the AO 112 to the inverting input “-” of the AO 112.

[0085] In the example shown, the inverting input “-” of the AO 112 is connected to the measuring electrode 102. The non-inverting input “+” of the AO 112 receives the working potential VT and is connected to the guard electrode 104. Under these conditions, the measuring electrode 102 and the guard electrode 104 are both at the working potential T.

[0086] Under these conditions, the AO 112 provides an alternating voltage output denoted Vs, which is proportional to the capacitive coupling between the measuring electrode 102 and the object O, and therefore proportional to the distance between the object O and the measuring electrode 102.

[0087] The measuring electronics 110 may further comprise a synchronous demodulator 116 making it possible to provide a useful signal V u by synchronous demodulation of the voltage V s provided by AO 112, with working potential T.

[0088] Furthermore, the measuring electronics 110 may further comprise a module 118 for calculating a measured coupling capacity Cm as a function of the useful voltage V u .

[0089] To do this, the calculation module 118 can use a calibration table linking the measured useful voltage Vu to the coupling capacitance, denoted Cm. Such a correspondence table can be determined during a calibration phase, for example.

[0090] In addition, the capacitive sensor 100 may further comprise a radial deflection calculation module 120 making it possible to provide a value of radial deflection DEF of a wheel as a function of the coupling capacity C and at least one first predetermined model.

[0091] The first model can be a calibration table, relating the value of the measured coupling capacitance C to that of the deflection DEF. Such a calibration table can be determined during a calibration phase.

[0092] Alternatively, the first model may be a predetermined mathematical relationship. For example, the mathematical relationship used may be a predetermined relationship of the type: C=a / (DEF+b) + k(l) with a, b and k constants related to the capacitive sensor and its configuration, determined during a calibration or calibration phase.

[0093] Furthermore, the sensor 100 may further comprise a load calculation module 122, using a second predetermined model, making it possible to provide a value of the load CH applied to the wheel as a function of the deflection value DEF.

[0094] The second model can be a calibration table, relating the deflection value DEF to the value CH. Such a calibration table can be determined during a calibration phase.

[0095] Alternatively, the second model may be a predetermined mathematical relationship. For example, the mathematical relationship used may be a predetermined linear relationship of the type: CH = Kz*DEF with Kz a coefficient of proportionality, also called vertical stiffness, which reflects the effect of load support by the pressure and by the sidewalls of the tire. The value of this stiffness, dependent on the pressure, can be determined by experience or calculated from models or tables. As a non-limiting example: Kz=KP+Ksw Kz=0.00028*P*V —0.004aR+1.03')SN*OD')+Ksw with - Kz the vertical stiffness of the tire in kg / mm, - Kp the stiffness linked to the tire pressure expressed in kg / mm, - Ksw the structural stiffness of the tire sidewalls expressed in kg / mm, - P the tire inflation pressure in Pa. - aR, without unit, the ratio between the width SN (mm) of the tire and its height, and - OD the outer diameter of the wheel (rim + tire) in mm.

[0096] FIGURES 2a-2g are schematic representations of non-limiting exemplary embodiments of electrode arrangements that may be implemented in the present invention.

[0097] FIGURE 2a shows a first example 210 of electrode arrangement viewed from above.

[0098] The arrangement 210 of FIGURE 2a includes only the measuring electrode 102 and the guard electrode 104.

[0099] In the example shown, and unlike the arrangement of FIGURE 1, the measuring and guard electrodes are coplanar.

[0100] FIGURE 2b shows another example of electrode arrangement viewed from above.

[0101] Arrangement 220 of FIGURE 2b includes: - the measuring electrode 102, - a first guard electrode 104i arranged under the measuring electrode 102, and - a second guard electrode 1042 arranged next to, and at the same level as, the measuring electrode 102.

[0102] FIGURE 2c shows another example of electrode arrangement viewed from above.

[0103] Arrangement 230 of FIGURE 2c includes: - the measuring electrode 102, - a first guard electrode 104i arranged under the measuring electrode 102, and - two other guard electrodes 1042 and 1043, arranged on either side of the measuring electrode 102, at the same level as the measuring electrode 102.

[0104] FIGURE 2d shows another example of electrode arrangement viewed from above. - the guard electrode 104, and - the measuring electrode 102, arranged in the guard electrode 104, so that the measuring and guard electrodes are concentric.

[0105] Optionally, the sensor may comprise another guard electrode disposed under the measuring electrode 102.

[0106] FIGURE 2e shows another example of electrode arrangement viewed from above.

[0107] Arrangement 250 of FIGURE 2e includes: - the measuring electrode 102, - a first guard electrode 104i arranged under the measuring electrode 102, and - a second guard electrode 1042, arranged in a comb, or interlaced, with the measuring electrode 102, at the same level as said measuring electrode 102.

[0108] FIGURE 2f shows another example of electrode arrangement viewed from the side.

[0109] Arrangement 260 of FIGURE 2f includes all of the elements of arrangement 220 of FIGURE 2b.

[0110] In addition, the arrangement 260 comprises another electrode 202, called the reference electrode. This reference electrode 202 is polarized at the working potential VT. In addition, this reference electrode 202 is positioned so that it is not sensitive to the presence of the object. In the example of FIGURE 2f, the reference electrode 202 is arranged between the guard electrodes 104i and 1042. According to other configurations, the reference electrode 202 can be arranged differently, for example under the guard electrode 104i, or next to and at the same level as the guard electrode 104i or between the measurement electrode 102 and the guard electrode 104. [YES] This reference electrode 202 can be used as a second measurement channel to correct drifts due to variation in temperature, humidity or pressure during capacitive measurements.

[0112] FIGURE 2g shows another example of electrode arrangement viewed from the side.

[0113] Arrangement 270 of FIGURE 2g includes all the elements of arrangement 230 of FIGURE 2c, viewed from the side.

[0114] In addition, the arrangement comprises another electrode 204, called an interaction electrode, used to reinforce the capacitive measurement. This interaction electrode 204 is arranged opposite the measurement electrode 102: - on the side and attached to the rim of the wheel when the measuring electrodes are placed on the side of the tire; or - on the side and attached to the wheel tire when the measuring electrodes are placed on the side of the wheel rim. This interaction electrode 204 is polarized at the ground potential M of the wheel.

[0115] Of course, such an interaction electrode can be used with any of the arrangements described above.

[0116] FIGURE 3 is a partial schematic representation of a first non-limiting example embodiment of a wheel according to the invention.

[0117] The wheel 300, shown in FIGURE 3, comprises a rim 302 and a tire 304 mounted on the rim 302. The tire 300 has a tread 306 contacting the ground

[0118] The wheel 300 further comprises a capacitive sensor according to the invention. In particular, the wheel 300 comprises the capacitive sensor 100 with the electrode arrangement 230 of FIGURE 2c. The capacitive sensor 100 is fixed integrally to the rim 302, with a fixing support 308, so that the measuring electrode 102 faces the tire 304, and in particular the tread 306 of the tire 304. When the wheel 300 is subjected to a radial deflection under the effect of a load, the tire 304 crushes and approaches the measuring electrode 102. The latter then detects and measures said radial deflection, by capacitive measurement.

[0119] According to an alternative configuration not shown, the capacitive sensor 100 can be attached to the tire 304, and in particular to an internal surface of the tire 304 at the tread 306. In this configuration, when the wheel is subjected to radial deflection under the effect of a load, the tire 320 crushes, which brings the measuring electrode 102 closer to the rim 302, so that the radial deflection is detected and measured by capacitive measurement.

[0120] FIGURE 4 is a partial schematic representation of another non-limiting exemplary embodiment of a wheel according to the invention.

[0121] The wheel 400 of FIGURE 4 comprises, like the wheel 300, a rim 302 and a tire 304 mounted on the rim 302. The tire 300 has a tread 306 coming into contact with the ground.

[0122] The wheel 400 further comprises a capacitive sensor 100 with the electrode arrangement 270 of FIGURE 2g. The capacitive sensor 100 is fixed integrally to the rim 302, with a fixing support 308, so that the measuring electrode 102 faces the tire, and in particular the tread 306 of the tire. The interaction electrode 204 is fixed on the inner face of the tire at the tread 306. When the wheel 400 is subjected to radial deflection under the effect of a load, the tire 304 crushes and approaches the interaction electrode 204 to the measuring electrode 102 which detects said radial deflection, by capacitive measurement.

[0123] According to an alternative configuration not shown, the measuring electrode can be attached to the tire, and in particular to an internal surface of the tire at the tread 306 and the interaction electrode 204 to the rim. In this configuration, when the wheel is subjected to radial deflection under the effect of a load, the tire crushes, which brings the measuring electrode 102 closer to the interaction electrode, so that the radial deflection is detected by capacitive measurement.

[0124] FIGURE 5a is a schematic representation of another non-limiting exemplary embodiment of a wheel according to the invention.

[0125] The wheel 500 of FIGURE 5 comprises a pair of capacitive sensors 100i and 1002. The capacitive sensors 1001-1002 are, in particular, arranged in opposite and symmetrical positions with respect to the axial direction 502 of the wheel 500.

[0126] In this configuration, one of the capacitive sensors, namely the 100i sensor, measures a radial deflection because it is on the ground side. The other of the sensors, namely the IOO2 sensor, does not measure any radial deflection because it is on the opposite side. Thus, a measurement by the 100i sensor will give a deflection value while a measurement by the IOO2 sensor will not represent any radial deflection. Therefore, the measurement made by the IOO2 sensor can be used to correct possible measurement drifts due to, for example, temperature, pressure, humidity, etc.

[0127] Opposite the part of the wheel in contact with the ground, called the lower part of the wheel, there is a counter-deflection of the wheel. The tread deviates from the rim by around 5 to 10% of the deflection experienced in the lower part. Depending on the sensor accuracy, it is possible to measure this counter-deflection or not. The measurement of the sensor on the opposite side, sensitive or not, allows the deflection value to be corrected. Obtaining the counter-deflection value also provides additional knowledge on the vertical stiffness of the tire, which depends directly on the inflation pressure.

[0128] According to embodiments, the sensors 100i and 1002 may be separated by an angle of 90° around the axial direction 502.

[0129] According to embodiments, the wheel according to the invention can be provided with several pairs of sensors, distributed for example according to a given angular pitch. Preferably, the sensors forming each pair of sensors are arranged in opposite or symmetrical locations relative to the axial direction of the wheel.

[0130] Each of the capacitive sensors IOO1-IOO2 may be the capacitive sensor 100 of FIGURE 1 with any of the electrode arrangements of FIGURES 2a-2g.

[0131] Optionally, each of the wheels 300, 400 and 500, and more generally the wheel according to the invention, may also comprise other sensors, for example at least one temperature sensor and / or at least one pressure sensor, which make it possible to recalibrate the relationships (models or tables) between the measured capacity and the deflection as well as the deflection and the load.

[0132] FIGURE 6 is a schematic representation of a non-limiting exemplary embodiment of a vehicle according to the invention.

[0133] The vehicle 600 of FIGURE 6 may be any type of vehicle having wheels, such as a bus, an airplane, a truck, a car, etc.

[0134] The vehicle 600 comprises several wheels 602, each equipped with at least one capacitive sensor according to the invention, and in particular the capacitive sensor 100 of FIGURE 1 with any of the electrode arrangements described above. For example, each of the wheels 6021-6022 may be any one of the wheels 300, 400 or 500 of FIGURES 3-5.

[0135] The vehicle 600 further comprises a module 604 for calculating the weight of the vehicle as a function of the load values ​​applied to each wheel. The calculation module 604 is connected, wired or wirelessly, to each of the capacitive sensors 100 of each wheel 602 of the vehicle 600. The module 604 receives from the capacitive sensor 100 of each wheel 602 a measured value of the load applied to said 602, and calculates the load or weight of the vehicle 600, for example by adding the loads measured by each capacitive sensor 100, or by using any other predetermined mathematical relationship.

[0136] FIGURE 7 is a schematic representation of a non-limiting exemplary embodiment of a method according to the invention for measuring the load applied to a wheel.

[0137] The method 700 of FIGURE 7 may be implemented in any of the wheels 300, 400, 500 or 602 of FIGURES 3-6.

[0138] The method 700 comprises a phase 702 of measuring the load of a wheel and which can be repeated as many times as desired.

[0139] The phase 702 of measuring the load of a wheel comprises a step 704 of measuring a radial deflection of the wheel.

[0140] Step 704 of measuring the radial deflection of the wheel comprises a step 706 of measuring a capacitance, called coupling, representative of said deflection, as described above, and in particular with reference to FIGURE 1, using a capacitive sensor. The radial deflection of the wheel approaches the measuring electrodes of the capacitive sensor of the tire, or of the rim or even of an interaction electrode, which modifies the capacitance seen by said measuring electrodes.

[0141] Step 704 includes a step 708 of calculating the radial deflection from the coupling capacitance measured in step 706, using a first predetermined model which may be a lookup table or a mathematical relationship.

[0142] The load measurement phase 702 further comprises a step 710 of calculating the load applied to the wheel, from the deflection value obtained in step 708, using a second predetermined model which may be a correspondence table or a mathematical relationship.

[0143] Optionally, but particularly advantageously, the charge measurement phase 702 may comprise a step 712 of correcting the measured coupling capacitance, with a capacitance value obtained by a measurement channel using for example - a reference electrode as described with reference to FIGURE 2f, or - another capacitive sensor forming, with the capacitive sensor used in step 706, a pair of sensors as described with reference to FIGURE 5. Optional step 712 then provides a corrected value of the coupling capacitance and used during step 708 of calculating the radial deflection of the wheel.

[0144] The method 700 may further comprise an optional calibration phase 720, making it possible to determine the first and second models by testing.

[0145] FIGURE 8 is a schematic representation of a non-limiting exemplary embodiment of a method according to the invention for measuring the weight of a vehicle.

[0146] The method 800 of FIGURE 8 can be implemented in any vehicle according to the invention and in particular in the vehicle 600 of FIGURE 6.

[0147] The method 800 includes a phase 802 of measuring the weight of the vehicle and which can be repeated as many times as desired.

[0148] The measuring phase 802 comprises a step 804 of measuring a load applied to each wheel of the vehicle, for example using the method 700 of FIGURE 7 for each wheel of the vehicle individually.

[0149] Then, phase 802 comprises a step 806 of calculating the weight of the vehicle, from the load values ​​applied to the wheels measured in step 804 and using a third predetermined model which may be a correspondence table or a mathematical relationship. For example, the third model may be an addition of the loads measured during step 804 for the wheels of the vehicle, with or without weighting.

[0150] Optionally, the method 800 may further comprise a calibration phase 810, making it possible to determine the third model by testing.

[0151] Of course, the invention is not limited to the examples which have just been described.

Claims

DEMANDS 1. Wheel (300;400;500) comprising a rim (302) and a tire (304) characterized in that it further comprises at least one capacitive sensor (100) for radial deflection of said wheel, said capacitive sensor (100) comprising: - at least one capacitive measuring electrode (102) disposed in said wheel (300;400;500) opposite said rim (302) or said tire (306); - at least one electrode (104; 1041-1043), called a guard electrode, to electrically guard said at least one measuring electrode (102); and - a measurement electronics unit (110) for: ■ polarize said electrodes at an alternating electrical potential, called the working potential, different from a potential of said wheel (300;400;500), at a frequency, called the working frequency, and ■ measure an electrical signal (V S ,V U), said measurement signal, relating to the capacitance seen by said measuring electrode (102) and representative of the radial deflection of said wheel (300;400;500).

2. Wheel (300;400;500) according to the preceding claim, characterized in that at least one capacitive sensor (100) comprises at least one guard electrode (104,1042, 1043) and at least one measuring electrode (102) coplanar.

3. Wheel (300;400;500) according to any one of the preceding claims, characterized in that at least one capacitive sensor (100) comprises a guard electrode (104) disposed under a measuring electrode.

4. Wheel (300;400;500) according to any one of the preceding claims, characterized in that at least one capacitive sensor comprises at least one measuring electrode (102i) and at least one guard electrode (1042): - intertwined or comb-like, and / or - concentric 5. Wheel (300;400;500) according to any one of the preceding claims, characterized in that at least one capacitive sensor comprises at least one electrode (202), said to be a reference electrode, arranged so as not to be sensitive to a radial deflection of said wheel (300;400;500).

6. Wheel (300;400;500) according to any one of the preceding claims, characterized in that at least one capacitive sensor comprises an electrode (204), referred to as an interaction electrode: - polarized to the wheel potential (300;400;500), - arranged in solidarity with the tire (304), opposite the measuring electrode (102) arranged on the rim (302).

7. Wheel (300;400;500) according to any one of the preceding claims, characterized in that at least one capacitive sensor comprises: - a first module (120) for calculating a deflection value (DEF), and / or - a second calculation module (122) for a charge value (CH m) applied to said wheel (300;400;500).

8. Wheel (300;400;500) according to any one of the preceding claims, characterized in that it comprises at least one electrical source delivering the working potential (VT) to at least one capacitive sensor.

9. Wheel (3500) according to any one of the preceding claims, characterized in that it comprises several capacitive sensors (IOO1-IOO2) distributed around the axial direction (502) of said wheel (500), possibly associated in pairs.

10. vehicle (600) equipped with at least one wheel (6021-6022) according to any one of claims 1 to 9.

11. Vehicle (600) according to the preceding claim, characterized in that it comprises: - several wheels (6021-6022) according to any one of claims 1 to 9, and - a module (604) for calculating the weight of said vehicle. (600) 12. A method (700) for determining a load applied to a wheel (300;400;500), in particular to a wheel according to any one of claims 1 to 9, comprising at least one iteration of a measurement phase (702) comprising the following steps: - measurement (706) of a measurement signal relating to a radial deflection of said wheel (300;400;500) by at least one capacitive sensor (100) disposed in said wheel (300;400;500), and - calculation (708) of a value of a load applied to said wheel(300;400;500), as a function of said measurement signal and a predetermined load calculation model.

13. A method (800) for determining the weight of a vehicle comprising several wheels, in particular wheels according to any one of claims 1 to 9, said method (800) comprising at least one iteration of a weight calculation phase (802) comprising the following steps: - measurement (804) of load values ​​applied to several wheels (6021-6022) of said vehicle (600) by the method (600) according to the preceding claim; and - calculation (806) of a weight of said vehicle (600) from said load values ​​and a predetermined weight calculation model.

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