WO2016096662A1

WO2016096662A1 - System and method for evaluating the contact area of a tyre

Info

Publication number: WO2016096662A1
Application number: PCT/EP2015/079455
Authority: WO
Inventors: Thomas Ledoux; Denis Martin; Guillaume HEREDIA; Alexandre PERNOT
Original assignee: Compagnie Generale Des Etablissements Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2014-12-17
Filing date: 2015-12-11
Publication date: 2016-06-23
Also published as: FR3030742A1

Abstract

The invention relates to a system for evaluating the contact area of a vehicle, said system comprising: a system for evaluating the condition of a tyre, comprising a casing that is positioned on the ground; means for determining at least one instant at which the vehicle passes over a distinct passage point of the casing of the evaluation system; and means for calculating at least one local contact area length of at least one tyre of the vehicle according to the passage of the vehicle and dimensional data of the casing and/or the vehicle and the speed of the vehicle.

Description

System and method for evaluating the contact area of a tire

FIELD OF THE INVENTION

The present invention relates to a system for evaluating the contact area of a tire, and the boom of a tire.

[0002] By evaluation of contact area, or tire-floor contact zone, is meant the evaluation of one or more parameters concerning the contact area, among which the shape of this area, its surface and its different dimensions.

The deflection of a tire is defined by the radial deformation of the tire, or variation of the radial height, when it moves from an uncharged state to a statically loaded state, under load conditions and nominal pressure.

The deflection measurement is a size commonly used to estimate the severity of the operating conditions of a tire from the point of view of the endurance of the carcass. It is therefore useful to know this measure, especially for vehicle fleet managers or transport professionals. Indeed, in these activities, where the notion of cost is very important, it is useful to check the good conditions of use of the tires, in particular to allow multiple retreads of a tire. Indeed, an operation of the tire with excessive sagging can lead to premature fatigue of the cables constituting the carcass of the tire, and thus prevent the use of this carcass for future retreading. In this way, the replacement of the carcass comes later, which leads to a decrease in the cost price of tires per kilometer.

To meet this need, tire pressure monitoring devices are known, which are put in place to monitor that the sagging of the sidewalls of the tire at the level of the contact area remains as close as possible. optimal operating conditions.

However, this simple pressure monitoring does not guarantee good conditions of use, since the boom of a tire also depends on the load imposed on said tire. It is known, for example, that in certain professional applications, in particular the transport of solid bulk materials, excessive loads are exerted on the tire, causing excessive sagging. The present invention is therefore to provide a system for evaluating the contact area of a tire to overcome these drawbacks.

BRIEF DESCRIPTION OF THE INVENTION

The invention relates to a system for evaluating the contact area of a vehicle, the system comprising:

a system for evaluating the state of a tire comprising a casing placed on the ground, means for determining at least one transit time of the vehicle on a point of passage of the casing of the evaluation system, and means for calculating, as a function of the passage time of the vehicle and the speed of the vehicle, at least one length of local contact area of at least one tire of the vehicle.

[0009] Preferably, the system for evaluating the state of a tire is a wear measurement system comprising a housing placed on the ground in which are advantageously installed:

A device for detecting the wear of a tire,

A device for detecting the presence of a tire on the casing, and

Electronic means for activating the wear detection device when detecting the presence of a tire.

The wear detection device preferably implements a sensor placed inside the housing, close to a face of the housing intended to be in contact with the surface of the tire, and capable of measuring the distance which separates said sensor from the metal reinforcements constituting the tire.

The sensor comprises for example a static or alternating magnetic field source and an adjacent sensitive element, the source being a coil or a permanent magnet and the sensitive element a sensor whose output signal can, for example, be function level the local magnetic field of induction. In this case, the sensing element is positioned so that the intensity of the magnetic field varies as the distance decreases. The sensitive element is preferably selected from the group of Hall effect or magnetoresistive sensors.

In another example, the sensor may be an eddy current sensor.

In another embodiment, the system for evaluating the state of a tire of the vehicle comprises in particular a measuring device, for example measuring the pressure of a tire, or measuring any other characteristic. of a tire.

Preferably, the evaluation system of the contact area is such that the means for measuring a transit time of the vehicle on a passage point of the housing of said evaluation system comprise a line of sensors. installed perpendicular to the direction of travel of the vehicle on the housing. The sensors used for this purpose are, for example the sensors of a wear measuring device, as explained previously.

Preferably, the evaluation system of the contact area comprises means for calculating the speed of the vehicle.

For example, the speed is calculated as a function of the passage time of the vehicle on the casing of the evaluation system of the state of a tire, and dimensional data of the casing and / or the vehicle.

In a particular embodiment, the evaluation system of the contact area comprises means for storing the dimensional data of the housing used for calculating the speed. These dimensional data include, but are not limited to, projected distances between different elements incorporated in the housing, for example piezoelectric sensors, piezoelectric cables, or electrodes coated with piezoelectric paint. By "projected distance" is meant here the distance between the respective projections of the elements on the same plane, parallel to the ground on which rolls the vehicle whose speed is calculated.

In a particular embodiment, the evaluation system of the contact area implements means of identification of the vehicle, useful for calculating the speed. These means are, for example, an RFID reader, integrated in or on the housing, or nearby. Such a reader can not read the identifier of a RFID chip intested in one or more vehicles nneus or affixed to the chassis of said vehicle. This RFID reader is preferably linked by telecommunications means to a remote database making it possible to establish a link between an RFID identifier and a tire and / or a vehicle. In this way, it is possible to exchange dimensional information about the identified vehicle with said remote database. The dimensional information includes, for example, the tire size, the wheelbase, the front track or the rear track of the vehicle.

In a particular embodiment, the evaluation system of the contact area implements the device for detecting the presence of a tire belonging to the system for evaluating the state of a tire, in order to allow the calculation of the speed. Said device for detecting the presence of a tire comprises at least one element included in the group comprising: a ferroelectret type sensor (PP, CYTOP, etc.), an organic piezoelectric sensor, a cable and / or piezoelectric fiber, a transducer piezoelectric, a piezoelectric bimetallic strip or a sensor made in the form of an inorganic piezoelectric composite applied to a support. The piezoelectric composite may, for example, be a paint supplemented with barium titanate, an oxide known for its ferroelectric properties. Any other element having ferroelectric properties, such as for example and non-exhaustively, TGS, PZT, BST, KNbO3, LiNbO 3, LiTaO 3, could be used as an additive to a conventional paint to form a usable piezoelectric composite. in the context of this device.

In another particular embodiment, the tire presence detection device comprises at least one element included in the group comprising: an accelerometer, an omnidirectional vibration or tilt sensor (for example of the SQ-SEN-200 type of the company SignalQuest) or a strain gauge glued to a point of the structure of the housing. Preferably, the system further comprises means for determining several local contact area lengths for each vehicle tire, each length of local contact area being determined as a function of the time of passage of the vehicle. pneumatic on a sensor line sensor.

Preferably, the system comprises means for reconstituting the tire contact area shape as a function of the local contact area lengths of said tire. In one example, these reconstitution means comprise means for transmitting local contact lengths to a remote server.

In another example, these reconstitution means furthermore comprise means allowing the temporal registration of the local contact area lengths relative to each other, as a function of a time shift introduced at the time of the determination of the corresponding passage times at each length of local contact area.

The invention also relates to a method of evaluating the contact area of a vehicle passing over a housing of a system for evaluating the state of a vehicle tire, the method comprising the steps following:

the step of determining at least a transit time of the vehicle on a point of passage of the system housing of the evaluation system, and

the step of calculating, as a function of the passage time of the vehicle and of the size data of the housing and / or of the vehicle and the speed of the vehicle, at least one length of local contact area of at least one tire of the vehicle .

The system for evaluating the state of a tire of the vehicle comprises in particular a measuring device, for example measuring wear, or measuring pressure, or measuring any other characteristic of a tire. pneumatic.

In a particular embodiment, the method comprises the step of reconstructing a form of contact area from the determination of several lengths of local contact area from the same tire.

In a particular embodiment, the method is such that it comprises the step of determining at least two times of passage of the vehicle on two passage points of the housing.

The steps of determining a first and second time of passage of the vehicle on the housing consist of the detection of the passage of the same wheel at two different points of the housing. Thus, for example, it is possible to detect the passage of a wheel on an activation device of the measuring device and the passage of the same wheel on the measuring device. It is also possible to detect the passage of a wheel on two elements of a tire presence detection device, the elements being included in the group comprising: piezoelectric sensors, piezoelectric cables, or electrodes covered with a piezoelectric paint, or any other element sensitive to local deformation of the housing structure constituting the measuring system.

In another particular embodiment, the method is such that the steps of determining a first and second moments of passage of the vehicle on the housing consist of detecting the passage of two separate axles of the vehicle at a single point of the housing . This single point may be, for example, the measuring device, or the activation device of the measuring device.

In another particular embodiment, the method is such that the steps of determining a first and second moment of passage of the vehicle on the housing consist respectively in the detection of a shock on the housing and in the detection of a passage of a wheel. In this case, the detection of a shock can be ensured, for example, by any sensor sensitive to shocks, such as accelerometers, SQ-SEN-200 sensors of the company SignalQuest, piezoelectric buzzers, gage gauge. stress or sensors based on piezoelectric composites glued at a single point of the housing structure.

In another embodiment finally, the first moment of passage corresponding to the detection of a shock on the housing, it is possible to detect said first instant with more accuracy by correcting the propagation time of the wave of shock in the material constituting the housing of the evaluation system. To do this, the correction is a function of the rigidity of the material.

In addition, the invention also relates to a system for evaluating the state of a tire, comprising one or more of the following means: means for determining the deflection of the tire as a function of the area of contact of the tire. means for determining the tire pressure as a function of the contact area of the tire and a known load applied to the tire. means for determining the load applied to the tire as a function of the contact area of the tire and the tire pressure. DETAILED DESCRIPTION OF THE INVENTION

Other advantages and embodiments of the invention will become apparent with the detailed description of the figures, made without limitation, in particular

FIGS. 1a and 1b which show two views of an evaluation system according to the invention, FIG. 2 which shows a signal measured at the output of a system according to the invention, FIG. 3 which shows a surface of contact area determined by a system according to the invention, and

Figure 4 which shows the relationship between the contact area of a tire and the deflection of the tire.

The system shown in FIGS. 1a and 1b consists of:

a housing 10 consisting of two access ramps 15 and a horizontal wear measurement zone located between the two access ramps 15.

two tire presence detection devices each consisting of three piezoelectric sensors 110, positioned along a line transverse to the direction of travel of a vehicle arriving on the housing. In this example, the piezoelectric sensors are buzzers stuck on the structure of the housing 10.

a line of wear measurement sensors 100 positioned along a line transverse to the direction of travel of the vehicle arriving on the housing 10. These wear measuring sensors can be indifferently sensors with variable reluctance , or eddy current sensors. Alternatively this line of electromagnetic wear sensors can be replaced by an optical wear measurement system applying the principle of laser triangulation.

a processing electronics 140 on which are connected the wear measurement sensors 100 and the presence detection sensors 110. In this example, the processing electronics 140 also contains an RFID reader for reading RFID chips embedded in the tires or glued to the vehicle whose speed, and tire wear, are measured. During the passage of a tire 20 on the housing 10 of the wear measuring system, the presence of the tire is first detected by a first tire presence detection sensor line, then, when the pneumatic leaves the housing 10 of the wear measuring system, its presence is detected by a second line of tire presence detection sensors. The distance between the two tire presence detection devices being known, it is then possible to calculate the speed of the tire by a very simple formula: Average speed = d / tO

In this formula, the distance d is the distance separating the two transverse lines of tire presence detection sensors 110, and the time t 0 is the time elapsed between the detection of the presence of the tire by any one of the sensors belonging to the first tire presence detection sensor line 110 and detecting the presence of the tire by any one of the sensors belonging to the second tire presence detection sensor line 110.

FIG. 2 shows, in continuous and discontinuous lines, examples of signals measured at the output of two different wear measuring sensors 100, during the passage of a tire vertically from said sensors for measuring the wear. 100 wear.

The speed of the tire being known, it is then very easy to measure the local length of the contact air of the tire, vertically to the wear sensor considered. In the case of the sensor whose output signal is represented in solid lines, the formula to be applied is:

Local ADC Length = Average Speed * t = d * t / t0

In this formula, the value of the time t is measured by means of the processing electronics 140 which is, for example, provided with a threshold detection. The time t is then the time elapsing between the first threshold crossing 40 by the output signal of the wear measurement sensor considered, and the second threshold crossing 50 by the output signal of the measurement sensor of the wear considered. As indicated above, in an exemplary embodiment, a line of wear measurement sensors 100, installed perpendicular to the running direction of the vehicle, is used to measure the wear of the tires during the passage of a tire. vehicle. The sensors components of this line of wear measuring sensors 100 advantageously being sufficiently close to each other, it is possible to carry out several wear measurements in the width of the contact area.

For example, in the case of a tread of twenty centimeters wide, if the sensors are arranged every two centimeters along a line transverse to the rolling direction of the tire, at least nine sensors will be able to achieve a wear measurement in the width of said tire. In this case, nine measures of local length of contact area can be made as described above.

Once the local length measurements have been made, they are for example transmitted to a remote server by using transmission means, for example by radio frequency, integrated with the processing electronics 140. It is then possible to implement means to reconstruct the shape of the contact area, and exploit this form, for example by exposing it on a website to a fleet manager vehicles. Figure 3 shows an example of contact area 60 reconstituted by this method. In this example, the tire concerned has a sufficiently wide tread to allow the realization of five local length measurements of the contact area in the width of the contact area of said tire.

In this example, the lengths d1, d2, d3, d4 and d5 are the local contact area lengths measured using the wear sensors, as described in the example of FIG. 2.

When the arrival of a tire on the system described in Figures 1a and 1b, the output signals of the sensors 100 useful for the measurement of wear because arranged facing the contact area of the tire , will not all pass simultaneously threshold 40 marked in FIG. 2. This time shift t1 is illustrated in FIG. 2, between the two output signals 30.

Similarly, these output signals 30 will not cross simultaneously the threshold 50 identified in Figure 2. In the case shown in Figure 2, there is a time t2 that flows between the two crossings of thresholds 50.

This is explained by the shape of the contact area of the tires, which is not always a perfect rectangle, but may, for example, have a more rounded shape, for example in its front part 65 and in its rear portion 66, as shown in the drawing of Figure 3. [0051] In this case, for the reconstruction of the contact area, it is useful to take into account these time differences tl and t2 between all of output signals of the wear sensors, so that the actual shape of the contact area can be correctly represented as is the case in Figure 3.

In FIG. 3, the local contact area lengths d5 and d4 correspond to the output signals 30 shown in FIG. 2. The curve 30 in continuous line corresponding to the length of the local contact area d4 and the curve 30 in broken lines corresponding to the length of local contact area d5. To illustrate the effect of the time offsets t1 and t2 of FIG. 2, on the geometry of the contact area 60, the offsets t1 and t2 of FIG. 2 are reported in FIG. 3. the invention also relates to an evaluation system for determining the deflection of a tire. This determination is made using a known relationship between a measured contact area length and the deflection of a tire. Figure 4 illustrates an example of such a relationship in the case of a truck tire.

This relationship, obtained by finite element calculation means shows that the link between the arrow and the contact area length is linear around the nominal operating area of the tire. For example, for a heavy-duty tire requiring an inflation pressure of 9 bar, this relation is valid for pressures varying between 4 bars and 15 bars. Thus, when the wear measurement system described in FIGS. 1a and 1b transmits the contact area length information to a remote database, it is possible to use such a relationship for convert this information into an arrow value of the tire. This can be done because the tire is identified by means of the RFID reader positioned in the processing electronics 140 visible in Figure 1b.

This is a real advantage because it allows to give directly to a user of the vehicle, or to a fleet manager, an arrow measurement, which is the size commonly used to judge the severity of the tire operating conditions. from the point of view of the endurance of the carcass.

Claims

A system for evaluating the area of contact of a vehicle, the system comprising:

a system for evaluating the state of a tire comprising a casing placed on the ground, means for determining at least one transit time of the vehicle on a point of passage of the casing of the evaluation system, and calculation means, as a function of the passage time of the vehicle and the speed of the vehicle, at least one length of local contact area of at least one tire of the vehicle.

The system for assessing the area of contact of a vehicle according to claim 1, further comprising means for calculating, as a function of the transit times and dimensional data of the housing and / or the vehicle, a speed of passage of the vehicle. vehicle on the case.

Evaluation system according to one of the preceding claims, wherein the means for determining a passage time of the vehicle on a point of passage of the evaluation system housing comprise a sensor line installed perpendicularly to the direction of travel of the vehicle on the case.

Evaluation system according to claim 3, comprising means for determining several local contact area lengths for each tire of the vehicle, each local length being determined as a function of the time of passage of the tire on a sensor of the sensor line .

5. Evaluation system according to claim 4, comprising means for reconstituting the tire contact area shape as a function of the local contact area lengths of said tire.

An evaluation system according to claim 5, wherein the reconstitution means comprises means for transmitting local contact lengths to a remote server.

An evaluation system according to claim 5 or 6, wherein the reconstitution means further comprises means for geometrically resetting the local contact area lengths with respect to one another based on a time lag. introduced at the time of the determination of the passage times corresponding to each length of area.

8. A method of evaluating the contact area of a vehicle passing on a casing of a system for evaluating the state of a tire of the vehicle, the method comprising the following steps:

the step of determining at least a transit time of the vehicle on a point of passage of the evaluation system housing, and

The method of evaluating the contact area of a vehicle according to claim 8, comprising the step of reconstructing a form of contact area from a plurality of predetermined local contact area lengths.

A tire condition evaluation system, comprising a tire contact area evaluation system according to one of claims 1 to 7, and further comprising means for determining the condition of a tire. the deflection of the tire according to the contact area of the tire.

A tire condition evaluation system, comprising a tire contact area evaluation system according to one of claims 1 to 7, and further comprising means for determining the condition of a tire. the tire pressure as a function of the contact area of the tire and a known load applied to the tire.

12. A system for evaluating the state of a tire, comprising a system for evaluating the contact area of a tire according to one of claims 1 to 7, and further comprising means for determining the state of the tire. the load applied to the tire as a function of the contact area of the tire and the tire pressure.