Rim for wheel with sensor and wheel comprising said rim

Abstract

A rim for wheel is described including a measuring system for detecting the vertical load applied to the wheel. The measuring system includes a sensor adapted to detect a deformation of the rim and to transmit a deformation signal to a processing unit. The processing unit receives an output signal of the sensor related to the deformation of the rim detected, and determines the vertical load applied to the wheel.

Claims

1. A rim for a wheel, including a measuring system to detect a vertical load applied to the wheel in operating conditions with wheel mounted with horizontal rotation axis, the measuring system comprising: a sensor to detect a deformation of the rim and to transmit a deformation signal related to the detected deformation, and a processing unit, operatively connected to the sensor, configured to receive the deformation signal, and to determine the vertical load applied to the wheel, based on the deformation of the rim detected by the sensor, the processing unit is configured to: store measurements made by the sensor and detects a first LMIN value of absolute minimum, a second LMAX value of absolute maximum and a Lt_med value of relative minimum of the deformation signal generated by said sensor during a rotation of the rim, and calculate the value of the vertical loads acting on the wheel, based on the detected a first LMIN value of absolute minimum, the second LMAX value of absolute maximum and the Lt_med value of relative minimum of the deformation signal generated by said sensor.

2. The rim according to claim 1, wherein the sensor is housed in a seat on a surface of the rim and the sensor is adapted to detect a deformation of said seat.

3. The rim according to claim 2, further comprising a plurality of spokes and wherein the seat is obtained on a spoke of the said plurality of spokes.

4. The rim according to claim 2, further including an annular element to house a tyre, and a frontal disc applied to the annular element, and wherein the seat is obtained on an area of the said disc that faces said annular element.

5. The rim according to claim 1, wherein the sensor is a capacitive type sensor comprising a pair of metal armatures and a dielectric material interposed between said metal armatures.

6. The rim According to claim 5, wherein this dielectric material is chosen in the group of materials comprising the following materials: cellulose acetate, copolymers, fluoropolymers, Polymers, Tedlar®.

7. The rim according to claim 1, wherein the processing unit is further adapted to calculate a value of the vertical load applied to the wheel according to the following formula: $\left[\begin{array}{c}{F}_V\\ F_L\end{array}\right]=\left[\begin{array}{ccc}{C}_{11}& C_{12}& C_{13}\\ C_{21}& C_{22}& C_{23}\end{array}\right]\left[\begin{array}{c}{L}_{\mathrm{MIN}}\\ L_{\mathrm{MAX}}\\ L_{t_{\mathrm{MED}}}\end{array}\right]$ where F.sub.V is said vertical load, F.sub.L is a lateral load applied to the wheel, the coefficients Cij, with i ranging between 1 and 2 and j between 1 and 3, are constant.

8. The rim according to claim 7, further comprising means for detecting pressure of a tyre mounted on said rim, and where the processing unit is configured to correct the value of the Cij coefficients as follows:
Cij′=Cij*k*P where Cij′ are the corrected Cij coefficients, P is the measured pressure value and k a predetermined constant.

9. The rim according to claim 1, further comprising means adapted to detect a temperature value of the tyre and wherein said processing unit is adapted to store measurements made by said sensor, and wherein the processing unit is further adapted to calculate a value of the vertical load applied to the wheel according to the following formula: $\left[\begin{array}{c}{F}_V\\ F_L\end{array}\right]=\left[\begin{array}{ccc}{C}_{11}& C_{12}& C_{13}\\ C_{21}& C_{22}& C_{23}\end{array}\right]\left[\begin{array}{c}{L}_{\mathrm{MIN}}\\ L_{\mathrm{MAX}}\\ L_{t_{\mathrm{MED}}}\end{array}\right]+\left[\begin{array}{c}{K}_1\\ K_2\end{array}\right]$ where F.sub.V is said vertical load, F.sub.L is a lateral load applied to the wheel, the coefficients Cij, with i ranging between 1 and 2 and j between 1 and 3, are constant, K.sub.1 and K.sub.2 are two values depending on said detected temperature value.

10. The rim according to claim 9, further comprising means for detecting pressure of a tyre mounted on said rim, and where the processing unit is configured to correct the value of the Cij coefficients as follows:
Cij′=Cij*k*P where Cij′ are the corrected Cij coefficients, P is the measured pressure value and k a predetermined constant.

11. A wheel comprising a rim including a measuring system to detect a vertical load applied to the wheel in operating conditions with wheel mounted with horizontal rotation axis, and a tyre mounted on that rim, the measuring system comprising: a sensor to detect a deformation of the rim and to transmit a deformation signal related to the detected deformation, and a processing unit, operatively connected to the sensor, configured to receive the deformation signal, and to determine the vertical load applied to the wheel, based on the deformation of the rim detected by the sensor, and wherein the processing unit is configured to: store measurements made by the sensor and detects a first LMIN value of absolute minimum, a second LMAX value of absolute maximum and a Lt_med value of relative minimum of the deformation signal generated by said sensor during a rotation of the rim, and calculate the value of the vertical load acting on the wheel, based on the detected a first LMIN value of absolute minimum, the second LMAX value of absolute maximum and the Lt_med value of relative minimum of the deformation signal generated by said sensor.

12. The wheel according to claim 11, wherein the sensor is housed in a seat on a surface of the rim and wherein the sensor is adapted to detect a deformation of said seat.

13. A vehicle comprising a wheel, said wheel comprising a rim including a measuring system to detect a vertical load applied to the wheel in operating conditions with wheel mounted with horizontal rotation axis, and a tyre mounted on that rim, the measuring system comprising: a sensor to detect a deformation of the rim and to transmit a deformation signal related to the detected deformation, and a processing unit, operatively connected to the sensor, configured to receive the deformation signal, and to determine the vertical load applied to the wheel, based on the deformation of the rim detected by the sensor, and wherein the processing unit is configured to: store measurements made by the sensor and detects a first LMIN value of absolute minimum, a second LMAX value of absolute maximum and a Lt_med value of relative minimum of the deformation signal generated by said sensor, and calculate the value of the vertical load acting on the wheel, based on the detected a first LMIN value of absolute minimum, the second LMAX value of absolute maximum and the Lt_med value of relative minimum of the deformation signal generated by said sensor, and wherein the measurement system comprises a wireless transmitter module to transmit measurements of the load acting on the wheel, and wherein the vehicle comprises a remote unit adapted to receive said measurements of the load acting on the wheel.

14. The vehicle according to claim 13, wherein the sensor is housed in a seat on a surface of the rim and wherein the sensor is adapted to detect a deformation of said seat.

15. The vehicle according to claim 13, further comprising a plurality of actuators, wherein the remote unit uses the measurements of the load acting on the wheel to control at least one actuator of said plurality of actuators.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the present invention will be more evident from the following description of some preferred embodiments thereof made with reference to the appended drawings.

(2) The different features in the individual configurations can be combined with each other as preferred according to the previous description, should it be necessary to avail of the advantages resulting specifically from a particular combination.

(3) In such drawings,

(4) FIG. 1 illustrates a wheel according to an embodiment of the present invention;

(5) FIG. 2A illustrates a sensor inserted in a seat provided in the rim of the wheel of FIG. 1;

(6) FIG. 2B schematically illustrates a deformation of the rim and of the sensor of FIG. 2A when the wheel is subject to a vertical load;

(7) FIG. 3 illustrates the attenuation of the output signal of the sensor used in the wheel of FIG. 1 as the frequency and the dielectric material used changes;

(8) FIG. 4 illustrates the output of the sensor of FIG. 1 as a function of the rotation angle of the wheel;

(9) FIG. 5 illustrates the load variation measured by the sensor as a function of the rotation speed of the wheel;

(10) FIG. 6 is a table that shows the influence of the longitudinal load on the measurement of the vertical one;

(11) FIG. 7 illustrates the variation of the load measurement as the pressure increases;

(12) FIG. 8 illustrates the measurement of the vertical load when a vertical and a horizontal load are applied;

(13) FIG. 9 shows an alternative rim to that of FIG. 1;

(14) FIG. 10A shows one of several different alternative embodiments for the armatures of a capacitive sensor;

(15) FIG. 10B shows one of several different alternative embodiments for the armatures of a capacitive sensor;

(16) FIG. 10C shows one of several different alternative embodiments for the armatures of a capacitive sensor;

(17) FIG. 10D shows one of several different alternative embodiments for the armatures of a capacitive sensor; and

(18) FIG. 10E shows one of several different alternative embodiments for the armatures of a capacitive sensor.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(19) In the following description, for the illustration of the figures, identical numbers or reference symbols are used to indicate construction elements with the same function. Further, for illustration clarity, some references may not be repeated in all the figures.

(20) While the invention is susceptible to various modifications and alternative constructions, certain preferred embodiments are shown in the drawings and are described hereinbelow in detail. It is in any case to be noted that there is no intention to limit the invention to the specific embodiment illustrated, rather on the contrary, the invention intends covering all the modifications, alternative and equivalent constructions that fall within the scope of the invention as defined in the claims.

(21) The use of “for example”, “etc.”, “or” indicates non-exclusive alternatives without limitation, unless otherwise indicated. The use of “comprises” and “includes” means “comprises or includes, but not limited to”, unless otherwise indicated.

(22) With reference to FIG. 1 a sectional view of a wheel 1 is illustrated according to an embodiment of the present invention. In the following description the wheel is considered in the mounted condition, i.e. with a horizontal rotation axis.

(23) The wheel 1 comprises in a known way a rim 2 on which a tyre 3 is mounted, and a measuring system able to measure a vertical load applied to the wheel in mounted conditions with a horizontal rotation axis.

(24) In the example of FIG. 1 the rim is of the type comprising a frontal disc 20 welded to an annular element 21 whose radial surface forms the so-called channel 22 intended to house the heel 30 of the tyre 3.

(25) The rim 1 is provided with a seat 23 in which a sensor 4 is housed that can detect deformations of the seat 23. Preferably the sensor 4 is a capacitive sensor, therefore provided with two conducting armatures 40 separated by a dielectric material 41.

(26) The dielectric material 41 can be of various types, however, preferred materials are cellulose acetate, copolymers, fluoropolymers, thermopolymers and Tedlar®. Experimental tests performed by the Applicant (see FIG. 3), have demonstrated that these materials have reduced signal attenuation (percentage less than 10%) for the frequencies of interest, comprised between 0 and 50 Hz, corresponding to the rotation frequency of the sensor mounted on a rim of 22″ of a vehicle that travels at a speed comprised between 0 and 130 km/h.

(27) As illustrated in FIG. 2A, in conditions of null load applied to the wheel, the two elements 21 and 22 which, facing each other, define the walls of the seat 23 of the sensor are not deformed and the output of the electric signal of the sensor is stable at a threshold value that indicates a null load condition. When, instead, the wheel is subjected to a load (FIG. 2B), the two elements 21 and 22 are deformed and with them the shape of the seat 23, so that the two armatures 40 of the sensor 4 move translating and rotating with respect to each other. Such movement of the armatures causes a deformation of the dielectric material 41 and, therefore, a variation of the electric signal generated by the sensor. The variation of the electric signal of the sensor therefore depends on the load applied to the wheel and its measurement can be used to measure the load on the wheel.

(28) Advantageously, the armatures of the capacitive sensor are shielded by means of a conductive layer, so as to reduce the noise coming from the vehicle, e.g. due to capacity due to contact between wheel and vehicle/ground.

(29) In the example of FIG. 1, the capacitive sensor 4 is mounted on a PCB that also houses an analog-to-digital converter 5. The output of the sensor 4 is connected to the input of the analog-to-digital converter (A/D) 5, which converts the analog signal at the output of the sensor 4 into a digital signal that is then sent, through appropriate wiring 10, to a storage and processing unit 6, which performs a first local processing of the measurement of the sensor 4 and supplies the data to a wireless transmitter module 7 which transmits them to a remote unit, not illustrated in the figure, but preferably mounted on board the vehicle, e.g. a car or truck, on which the wheel 1 is mounted.

(30) In the example of FIG. 1, the wireless transmitter 7 and the storage and processing unit 6 are housed in a case 8 that also houses an electric battery 9 able to supply the transmitter and all the other active elements of the system, such as the sensor 4, the A/D converter 5.

(31) Experimental tests, reported in FIG. 4, have made it possible to verify that by applying a constant vertical load to the wheel, as the latter rotates, the output signal of the sensor has a peak L.sub.MAX, when the sensor is located along the horizontal (values of 90° and 270° in the graphs of FIG. 4). The output signal of the sensor, instead, has an absolute minimum value L.sub.MIN when it is in the lowest part of the wheel (values of 0 and 360° in the graph of FIG. 4), and a relative minimum L.sub.t_med when it is in the highest point of the wheel (value of 180° in the graph of FIG. 4).

(32) Preferably, the absolute maximum L.sub.MAX, absolute minimum L.sub.MIN and relative minimum L.sub.t_med values are considered net of the disturbances and noise associated with the output signal of the sensor 4, as appears clear to a person skilled in the art from the example of FIG. 4. For example, the absolute maximum and minimum and relative values can be detected after filtering—such as lowpass filtering or bandpass filtering—of the output signal of the sensor 4, performed by the processing unit 6.

(33) The Applicant has therefore, empirically, discovered that the lateral F.sub.L and vertical F.sub.V forces acting on the wheel can be obtained according to the following formula (1):

(34) $\begin{array}{cc}\left[\begin{array}{c}{F}_V\\ F_L\end{array}\right]=\left[\begin{array}{ccc}{C}_{11}& C_{12}& C_{13}\\ C_{21}& C_{22}& C_{23}\end{array}\right]\left[\begin{array}{c}{L}_{\mathrm{MIN}}\\ L_{\mathrm{MAX}}\\ L_{t_{\mathrm{MED}}}\end{array}\right]+\left[\begin{array}{c}{K}_1\\ K_2\end{array}\right]& \left(1\right)\end{array}$

(35) wherein the coefficients Cij are constant and depend on the pressure of the tyre.

(36) In order to be able to calculate the vertical load F.sub.V and lateral load F.sub.L values, in a preferred embodiment the system for measuring the loads applied to the wheel also comprises means adapted to detect a pressure and temperature value of the tyre mounted on the rim. In one embodiment the means adapted to detect a pressure and temperature value comprise a sensor, e.g. a TPMS sensor, able to measure the inflation pressure of the tyre and the temperature of the air inside the tyre, the latter being connected to the temperature of the tyre itself.

(37) In particular, it is to be noted that although the use of a pressure sensor is preferable for measuring the pressure of the tyre, other systems may be used, which indirectly determine a pressure value by measuring other parameters. For example, the measurement of the distance between the rim and the tyre depends on the shape, but also on the pressure, of the tyre, so that differential measurements of the distance between the rim and the tyre can be considered indirect measurements of the tyre pressure.

(38) The means for detecting a pressure and temperature value of the tyre mounted on the rim can be mounted on the wheel, or be means already provided on the vehicle that mounts the wheel. In this case the storage and processing unit 6 can receive the pressure and temperature data from the remote unit of the vehicle through the wireless interface 7 that operates both as a transmitting module, as previously described, and as a receiving module for receiving data and/or controls from the remote unit of the vehicle.

(39) In general, the coefficient values Cij can be empirically measured. The Applicant has verified that in tyre pressure conditions of 4 bar and temperature of 20° C. the following values are recorded:
C.sub.11=−1.12.Math.10.sup.−1; C.sub.12=−1.58.Math.10.sup.−2; C.sub.13=1.28.Math.10.sup.−1;
C.sub.21=−5.33.Math.10.sup.−2; C.sub.22=−3.57.Math.10.sup.−2; C.sub.23=8.9.Math.10.sup.−2;

(40) In general, in usual operating conditions of a wheel, i.e. T comprised between −15° C. and T=45° C., and tyre pressure p comprised between 3 and 4.5 bar (commercial vehicle), the values mentioned above can vary by ±10%.

(41) Although slightly less accurate, given that the temperature drift is not very important in formula (1), in an embodiment that does not require any temperature sensor, the values K.sub.1 and K.sub.2 can be assumed to be equal to zero in formula (1). Through experimental tests, the Applicant has also verified the existence of a linear relationship between the pressure of the tyre P and the coefficients Cij. The graph of FIG. 7 shows how, with the same vertical load applied, as the pressure increases the load value measured by the sensor also increases.

(42) Therefore, the processing unit 6 is preferably configured to correct the value of coefficients Cij of formula (1) as follows:
Cij′=Cij*k*P

(43) where P is the pressure and k is the experimental correlation coefficient that determines the sensitivity of the sensor to the pressure. Preferred values of k are comprised between 1.Math.10.sup.4 and 2.Math.10.sup.4. In general, the value of k can however be defined during the manufacturing of the wheel and be stored in a storage area of the storage and processing unit 6. In one embodiment, the storage and processing unit 6 can comprise different values of k stored in a comparison table where, for different types of tyre and tyre pressure, a predetermined value of k is associated. At the time of mounting the wheel on the vehicle, the mechanic can interface with the storage and processing unit through an appropriate user interface (e.g. a remote control terminal that communicates in Bluetooth to the unit 6) for selecting the value of k.

(44) Experimental tests, reported in FIG. 8, have further demonstrated the effect of lateral forces on the measurement of the vertical force by the sensor that determine the ratio between the coefficients Cij.

(45) Operatively, therefore, as the wheel 1 turns, the armatures of the capacitive sensor 4 move with respect to each other deforming the dielectrics interposed between them. This implies a variation to the signal generated by the sensor which, under ideal conditions, is repeated cyclically at each rotation and that has an absolute maximum L.sub.MAX, an absolute minimum L.sub.MIN and a relative minimum L.sub.t_med. The processing unit 6 detects and stores these three values and calculates the values of the horizontal forces F.sub.L and vertical forces F.sub.V acting on the wheel.

(46) The processing unit 6 transmits at least the value of the vertical force F.sub.V, but preferably also the value of the horizontal force F.sub.O to the wireless transmitter 7.

(47) The signal transmitted by the transmitter 7 is received by a remote control unit that re-transmits the signal (possibly re-processed) to external devices (e.g. remote control units) and/or uses the information transported by such signal (i.e. F.sub.L and F.sub.V) for controlling actuators of the vehicle, e.g. for switching on alarm signals in the case of sudden variations of the load measured by a wheel.

(48) Experimental tests have made it possible to verify that the system described above is resistant to noise and other factors that can in some way affect the measurement.

(49) In particular, as illustrated in FIG. 5, the influence of the vehicle's translation speed is less than 4% and is random.

(50) Experimental tests have then made it possible to verify (see table in FIG. 6) that the influence of the longitudinal load on the measurement of the vertical one is less than 3%.

(51) Furthermore, as will be clear to a person skilled in the art, the system according to the embodiments of the present invention requires a single deformation signal for precisely identifying the horizontal forces F.sub.L and vertical forces F.sub.V acting on the wheel. This allows a system to be realized with extremely reduced dimensions and a single cable—for connecting the single sensor 4 to the storage and processing unit 6.

(52) In light of what is described above it is clear to a person skilled in the art how the invention allows the intended objects to be reached. In particular, the positioning of the sensor in a seat obtained in the rim of the wheel allows easy installation and facilitated access to the sensor in case of maintenance.

(53) Advantageously, the seat for the sensor is positioned in a point of the rim that is subject to the vertical load acting on the wheel, e.g. a portion of the channel for housing the tyre, or a spoke of a spoked rim. FIG. 9, for example, indicates different possible positions of a seat 23 for the sensor. Preferably, in case of spoked rims, a preferred position for the seat 23 is an area of the spoke that is located in the most external half of the spoke itself, i.e. in the proximal position of the channel.

(54) For example, despite the invention being described above with reference to a capacitive type sensor, it is clear that the sensor can also be of another type, e.g. optical or inductive sensors can be provided, which measure deformations of a seat obtained in the rim.

(55) Again, in the preferred solution of a capacitive condenser, it is clear that the sensor can have parallel plane armatures or also of another type. For example, the armatures can comprise parallel flat plane surfaces (e.g. FIGS. 10A and 10B) of any shape (e.g. rectangular as in FIG. 10A or elliptical as in FIG. 10B), or comprise curved plane surfaces (FIG. 10C), comprise semi-circular surfaces (FIG. 10E), have a constant thickness along the whole width thereof (e.g. FIG. 10A-10C) have a thickness ‘D’ that varies along the width, e.g. being maximum at the centre and minimum at the edges as in FIG. 10D.