Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
  • G01B7/26—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring depth
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M17/00—Testing of vehicles
  • G01M17/007—Wheeled or endless-tracked vehicles
  • G01M17/02—Tyres
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
  • G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
  • G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
  • G01B7/14—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring distance or clearance between spaced objects or spaced apertures
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
  • G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids

Definitions

• the present invention relates to a system for measuring the thickness of a rubber layer and more particularly to the measurement of the remaining rubber thickness of a tread of a tire. pneumatic tire.
• the tread of a tire is provided with a sculpture including elements of sculpture or elementary blocks delimited by various main grooves, longitudinal, transverse or oblique, the elementary blocks may further comprise various incisions or slices finer.
• the grooves are channels for evacuating water during a wet run and define the leading edges of the carving elements.
• the tread When a tire is new, the tread has its maximum height. This initial height may vary depending on the type of tire considered and the purpose for which it is intended; for example, "winter" tires generally have a greater tread depth than "summer” tires.
• the height of the elementary blocks of the sculpture decreases and the stiffness of these elementary blocks increases. Increasing the stiffness of the elementary blocks of sculpture results in a decrease in certain performances of the tire, such as wet grip.
• the water evacuation capacities decrease sharply when the depth of the channels of the sculptures decreases.
• Such monitoring is usually done by visual observation of the tread by the user or a garage with or without an effective measurement with a gauge. depth. But this observation is not very easy to achieve especially on the rear tires of access more difficult and is also not very accurate.
• the invention relates to a system for measuring the thickness of a layer of rubbery material of a tire, the layer having a face bonded to an adjacent reinforcement made with at least one magnetic permeability material greater than the magnetic permeability of the air and a free face in contact with the air, and the system comprising a housing with an application face intended to be in contact with the free face of the layer and a sensor placed in the housing capable of measuring the distance d between the bonded face and the free face of the layer of rubbery material.
• the sensor comprising an alternating magnetic field source and an adjacent sensitive element
• the source is a coil
• the sensitive element is a sensor whose output signal is a function of the level of the induction field magnetic local and in that the frequency and the excitation power of the source coil are such that the magnetic induction field increases between the adjacent armature and the source coil, when the distance d decreases.
• the sensor of the measuring system has the advantage of operating in reluctant mode, so with, given power, a coil excitation frequency lower than in the case of a similar sensor operating in an eddy current sensitive mode. It should be noted that in the case of conventional tire crown reinforcement, consisting of metal reinforcements embedded in a low-conductive rubber material, no or only weak eddy currents are detected under these operating conditions.
• the measurement in reluctant mode takes advantage of the magnetic permeability of the adjacent armature and it is found that this offers a high sensitivity of the measurements to any variation in the distance d.
• the sensitive element is a sensor selected from the group of Hall effect sensors, magneto-resistive.
• Hall effect sensors take advantage of a property of semiconductors which, when traversed by a current and applied to them a magnetic field perpendicular to the direction of movement of said current, see a voltage proportional to the magnetic field applied, measurable in the direction of this field. The measurement of this voltage then makes it possible to estimate the intensity of the magnetic field in which the semiconductor is immersed.
• Magneto resistive sensors take advantage of the property that semiconductors have a resistance that evolves when they are subject to a magnetic field. By subjecting such a material to a known electric current and by measuring the voltage across this material, it is then possible to estimate the intensity of the magnetic field in which the magneto-resistive material is immersed.
• the sensitive element is disposed between the source coil and the application face of the housing.
• the magnetic induction field measured by the sensitive element increases when the distance d decreases.
• the source coil is positioned between the sensitive element and the application face.
• the magnetic induction field measured by the sensitive element decreases when the distance d decreases.
• the sensitive element and the source coil can also be arranged adjacent and substantially at the same distance from the application face of the housing.
• the magnetic induction field measured by the sensitive element also decreases when the distance d decreases.
• the source coil is disposed around, or is surrounded by, a high electrical resistivity material and high magnetic permeability.
• this material with high electrical resistivity and high magnetic permeability such as a ferrite
• the sensor of the sensitive element is placed at the end of one of the branches of high electrical resistivity material and high magnetic permeability.
• the ferrite may be of various shape, in particular U-shaped.
• the excitation coil or source coil is then preferably arranged around one of the lateral branches of the U.
• the source coil can be arranged around the bottom of the U of the ferrite.
• the range of the sensor can be improved simply by increasing the distance between the two ends of the U.
• the source coil is disposed around a high electrical resistivity material and high magnetic permeability in the form of E.
• the source coil is advantageously arranged around the central bar of the E.
• the range of the sensor can be improved simply by increasing the distance between the central bar of the E and the two outer bars of it.
• This range can also be increased by increasing the section of the poles constituted by the three parallel bars of the E-shaped ferrite.
• the source coil is arranged around a material with high electrical resistivity and high magnetic permeability, the material having an axis of symmetry and in any axial section a shape of E.
• the source coil is advantageously arranged around the central axis of the high electrical resistivity material and high magnetic permeability, and the sensitive element is disposed at the end of the central axis of the pot.
• the range of the sensor can be improved simply by increasing the outer diameter of the potted structure, so that the distance between the central pole and the outer pole is greater.
• This range can also be increased by increasing the section of the two poles of the potted structure.
• This axisymmetric embodiment has the advantage of being insensitive to the orientation of the metal cables constituting the adjacent armature.
• the sensor is therefore insensitive to the anisotropy of this adjacent layer.
• This embodiment has the advantage of improving the sensitivity of the sensor, to simplify the control electronics and associated measurement and to reduce the cost.
• the material with high electrical resistivity and high magnetic permeability has an H-shaped shape.
• the H is disposed in the case with the normal lateral branches at the application face. of the case.
• the range of the sensor can be increased by increasing the distance between the two lateral bars of the H or by increasing the section of the poles constituted by these two lateral bars.
• the source may be a coil arranged around the central bar of the H.
• the source may also comprise two coils each arranged around a lateral branch of the H, preferably on either side of the central branch of the H.
• the source may also comprise four coils each disposed around a half-lateral branch of the H.
• the sensor of the sensitive element may comprise two sensors arranged each at one end of the same side branch of the H.
• the sensor of the sensitive element may also comprise two sensors each arranged on a separate lateral branch of the H, on either side of the central branch. It is also possible to use four sensors each disposed at each end of each half-side branch of the H.
• the local magnetic induction field measured on the one hand by the sensor (s) positioned at the upper ends of the H is equal to the measured local magnetic induction field, on the other hand, by the sensor or sensors positioned at the lower ends of the poles of H.
• the difference in output signal between these sensors is therefore low or zero.
• the two branches of the H are preferably placed in the direction of travel and each branch vertically, the measurement is then an average measurement of the distance between the sensor and the armature of the adjacent layer, related to the distance between the two arms of the H.
• the source may comprise one or more coils.
• the source coil is powered by an AC power source, preferably with a frequency of less than 500 kHz, then very strongly limits the generation of eddy currents in the adjacent frame of the layer. In addition, exceeding a frequency of 10 kHz, it eliminates conventional noise measured by a near-field antenna.
• the increase in frequency reduces the measurement time which has a favorable impact on the power consumption of the whole.
• the measuring system comprises a device for measuring the amplitude of the signal across the sensor or sensors of the sensitive element.
• the source coil can be powered by means of a known stationary sinusoidal current, which makes it possible to fix the measurable magnetic induction field in the vicinity of the sensor in a repeatable manner, and it is possible to use a measuring the amplitude of the voltage across the sensor or sensors constituting the sensitive element.
• This device for measuring the amplitude of the voltage across the sensitive element can continuously measure the voltage or use an amplitude demodulation system.
• the measuring system is advantageously arranged in a non-conductive electrical housing and whose materials have a magnetic susceptibility zero or low enough to be comparable to air or vacuum.
• the source coil having a sensitivity axis and the housing having an application face against the free face of the layer whose thickness is to be measured, the application face of the housing is normal or parallel to the sensitivity axis of the source coil according to the embodiment.
• the housing can be a portable housing.
• the measurement system according to an object of the invention can be applied to the measurement of the thickness of rubbery material of a sidewall or an inner liner of a tire. This measurement can be made during the manufacture of the tire or after the end of it.
• the housing can also be adapted to be disposed on or embedded in a driving floor.
• the measuring system is preferably applied to the measurement of the remaining rubber material thickness of a tread of a tire.
• each source coil of the measurement system may consist of a plurality of coils connected in series or in parallel.
• each of the source coils can be made in the form of conductive tracks wound spirally on a PCB or plastronic support.
• a plastronic support refers to a technology that allows the printing of conductive tracks and the attachment of electronic components directly to plastic parts obtained by injection.
• the invention is particularly applicable to tires having metal reinforcements in their apex and / or their carcass plies such as those intended to equip motor vehicles of tourism type, SUV ("Sport Utility Vehicles"), like vehicles.
• industrial vehicles selected from vans, "heavy goods vehicles” - that is, metros, buses, road transport vehicles (trucks, tractors, trailers), off-the-road vehicles such as civil engineering vehicles -, other transport or handling vehicles.
• FIG. 1 is a perspective view of a vehicle having a tire passes over a housing comprising a measuring system according to an object of the invention
• FIG. 2 shows a housing with a measuring system
• FIG. 3 shows a section of a tire in contact with the housing of the measuring system
• FIG. 4 shows the principle of operation of a measuring system in the case of an air coil, in the absence (a) and in the presence (b) of a metal plate;
• FIG. 5 shows schematically an example of operation of the measuring system in the case of an excitation coil with a U-shaped ferrite
• FIG. 6 shows an alternative embodiment of the system of FIG. 5
• FIG. 7 shows a second embodiment with an E-shaped ferrite
• FIG. 8 shows a third embodiment with a ferrite-shaped pot
• - Figure 9 shows an embodiment with an H-shaped ferrite; and - Figure 10 schematically shows a structure of the electronics of a measuring system.
• Figure 1 shows a vehicle 5 whose tire 8 rolls on a housing 6 having a wear measurement system.
• the figure shows a passenger vehicle but such a measurement system is also usable for any other vehicle, such as a truck or a bus.
• the measurement of the remaining thickness of rubber material of the tread of the tire 8 is made when the tire rolls over the casing 6 without it being necessary to stop the vehicle or disassemble the tire of the vehicle.
• FIG. 2 illustrates a housing 12 according to one of the objects of the invention. It is presented as a portable unit that can be placed on a taxiway. It has a substantially trapezoidal cross section.
• the housing comprises two inclined portions, an access ramp 15 and an outlet ramp 16. Between the two is a substantially horizontal portion 18.
• the portion 18 of the housing 12 protects a sensor or a row of sensors 50 for performing distance measurements.
• the base 20 of the casing is placed against the running ground and provides it with the necessary stability during operation of the system.
• the housing 12 also comprises an electronics 40 with a power source which supplies the sensors 50 with AC power. The measurements are made when the contact area of the tire rests on the horizontal portion 18. This horizontal portion is the face of the tire. applying the casing against the surface of the tread of the tire.
• the housing 12 is made of a non-conductive material whose magnetic properties are similar to those of air so as not to disturb the measurements.
• the housing can be embedded in a rolling floor or of suitable size and weight to be applied against a sidewall or an inner liner of a tire.
• FIG. 3 shows a partial section of a tire 8 resting on the application face 18. of a housing 12.
• the tire 8 comprises in particular a tread 80 with sculptures 82, a crown reinforcement 84 consisting of two or more plies of metal reinforcements (not shown), and flanks 86.
• the housing 12 comprises an application face 18, a base 20 and a row of sensors 50.
• the rolling surface 88 of the tread 80 bears against the application face 18 of the housing 12.
• the sensors 50 measure, as will be explained below, the distance D1 which separates them from the metal reinforcement 84 of the top of the tire 8.
• Dl has three components.
• the distance D2 can be known from the identification of the type of tire measured. This identification can be manual or automatic, for example by retrieving identification data entered in a transponder such as an RFID incorporated in the tire structure.
• FIG. 4 illustrates the operating principle of the sensor of a measurement system according to an object of the invention.
• FIG. 4 (a) shows an air coil 10 with an axis of symmetry and sensitivity A.
• the magnetic field lines 54 emitted by this device extend in the air all around the coil as shown schematically in FIG. 4 (a).
• FIG. 5 shows a schematic example of the operation of an embodiment of a measurement system in the case of an excitation coil and a U-shaped ferrite.
• the layer 21 whose thickness d is to be measured comprises a layer of rubber material 24 adjacent to a reinforcement 22 made up of reinforcements whose magnetic permeability is greater than the magnetic permeability of the air, such as those conventionally used for carcass plies or crown plies. of tires, in particular heavy goods vehicles.
• the housing 12 of the measuring system comprises a sensor 50 which comprises an excitation coil 10 arranged around one of the lateral branches 36 of a U-shaped ferrite 30 and a Hall effect sensor 56.
• the sensor 56 is placed at the end of the lateral branch 36 of the ferrite 30.
• the presence of the ferrite 30 makes it possible to locate the circulation of the magnetic field lines through it and thus to locate the measuring zone.
• the two bars of the U are distant from a distance 11.
• the housing 12 has its application face 18 bearing against the free face 26 of the layer 21.
• the frequency and the excitation power of the excitation coil 10 are such that the magnetic induction field between the ends of the poles of the ferrite 30 and the adjacent armature 22 increases as the distance d decreases.
• the mode of operation of the sensor is thus a reluctant mode thus related to the magnetic permeability of the different parts of the magnetic circuit.
• the magnetic permeability of the rubbery material is much lower than that of the adjacent reinforcement which is itself smaller than that of the ferrite.
• the reluctance of the layer 24 of rubbery material is much greater than that of the adjacent armature 22 which is itself greater than that of the ferrite 30.
• the magnetic induction field variation. measured at the ends of the ferrite 30 is mainly related to the variation of the thickness distance of the layer of rubbery material because any variation in the reluctance of the adjacent armature linked for example to the number of reinforcements or their construction does not. only a minor influence on the accuracy of the measurement. The accuracy and sensitivity of such a sensor reluctant mode are good.
• the range of the sensor is related to the distance 11, distance between the two bars of the U, and to the section of the poles constituted by these two parallel bars.
• FIGS 6 to 9 show alternative embodiments of sensors.
• the senor 60 comprises a U-shaped ferrite 64, an excitation coil 62 arranged around the central bar of the U and a Hall effect sensor 56 placed at the end of the one side branches of the U ..
• the sensor 70 comprises a ferrite 74 in the shape of an E, a coil 72 arranged around the central bar of the E and a Hall effect sensor 56 placed at the end of one of the lateral branches.
• the sensor 90 comprises a pot-shaped ferrite 94 with an axis of symmetry and a central bar disposed substantially along this axis of symmetry and an excitation coil 92 arranged around the bar. central of the pot. It also comprises a Hall effect sensor 56 disposed near the end of the central bar of the ferrite 94.
• FIG. 8 (a) shows a perspective view of the sensor and FIG. 8 (b) a section according to FIG. axis of symmetry.
• FIG. 9 shows another embodiment of a sensor 95.
• This sensor comprises an excitation coil 96 arranged around the central bar of a ferrite 97 in the shape of H. It also comprises two effect sensors. Halls 56 and 57 are each disposed at one end of the lateral bar 98 of the ferrite 97. The two sensors have the same measurement signal under free conditions. The difference of the two signals is therefore zero under these conditions. This makes it possible to totally or almost completely cancel the common mode and to improve the sensitivity of the sensor. The distance to be measured is then connected to this difference by a nonlinear law.
• FIG. 10 shows an example of the structure of the electronics for measuring the thickness of a rubber tire layer, in the case of a sensor consisting of a source coil 102 and an element.
• sensitive sensor 103 consisting of a single sensor for measuring the local magnetic field, or several sensors connected to each other.
• This electronics consists of a “sensor module” 100 and a “motherboard” 120. It therefore allows a layer thickness measurement at a single point.
• the "sensor module” 100 consists, among other things, of a current amplifier 104, driven by an oscillator 106 whose frequency is imposed by a time base. 107. Amplifiers, oscillator and timebase are part of the "sensor module".
• the voltage U, of phase ⁇ nonzero relative to the current I, taken at the terminals of the sensitive element 103, is first amplified by the amplifier 108 and then injected into a double demodulator 110, as well as the output signal of the oscillator 106.
• K is a factor related to the amplification present along the electronic chain.
• the two signals X and Y are then filtered by the filters 112 and digitized by means of analog / digital converters (ADC) 114 and then injected into the microcontroller 122 of the "motherboard" 120.
• ADC analog / digital converters
• the microcontroller 122 deduces from X and Y the value of the voltage U across the sensitive element 103 using the formula above.
• the motherboard is also provided with several additional functional blocks: a memory 124 to allow the recording of the measurements made by the sensor consisting of the source coil 102 and the sensitive element 103;
• An RFID decoder 126 which makes it possible to identify the tire, by means of an antenna 128, when this can be done by taking advantage of the presence of RFID incorporated in the structure of the tire;
• a wireless communication module 130 which makes it possible to send the information remotely via an additional antenna 132;
• a power supply 134 distributing the current required for the entire system, from a battery 136.
• the set has the ability to perform many measurements on tires, without changing batteries, which gives the system autonomy for several years without human intervention.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

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• 2013
  • 2013-07-26 FR FR1357411A patent/FR3009076B1/fr not_active Expired - Fee Related
• 2014
  • 2014-07-25 CN CN201480042163.4A patent/CN105431706A/zh active Pending
  • 2014-07-25 WO PCT/EP2014/066019 patent/WO2015011260A1/fr not_active Ceased
  • 2014-07-25 EP EP14744818.7A patent/EP3025120A1/de not_active Withdrawn
  • 2014-07-25 JP JP2016528544A patent/JP2016529494A/ja active Pending
  • 2014-07-25 US US14/907,186 patent/US10876826B2/en active Active

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