EP2435705A2

EP2435705A2 - Wheel

Info

Publication number: EP2435705A2
Application number: EP10724009A
Authority: EP
Inventors: Thierry Hilt; Bruno Mourey
Original assignee: Commissariat a lEnergie Atomique CEA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2009-05-25
Filing date: 2010-05-25
Publication date: 2012-04-04
Also published as: WO2010136472A3; EP2435706B1; JP2012528264A; WO2010136472A2; JP5587988B2; EP2435706A2; JP5718321B2; US8607627B2; WO2010136470A3; US8764422B2; JP2012528559A; WO2010136470A2; FR2945835A1; FR2945835B1; US20120067116A1; US20120068474A1

Abstract

This wheel is equipped with a tyre and an electric device (100), which needs to be supplied with power in order to operate. The device comprises a system (200) for converting the difference in pressure between the pressurized gas inside the tyre and the free air outside the tyre into electric power used for supplying the electric device.

Description

WHEEL

[001] The invention relates to a wheel.

[002] The wheels equip vehicles such as motor vehicles. [003] Known wheels are equipped with a tire and an electrical device that needs to be powered to operate

[004] Typically, the electrical device is a sensor of the pressure difference between a confined gas under pressure inside the tire and the free air present outside the tire. Such a sensor makes it possible to signal to the driver a wheel insufficiently inflated or punctured.

[005] Generally, to protect this electrical device, it is housed inside the tire. It is then difficult to connect it electrically to the battery of the motor vehicle to power it. It is also difficult to power this device from batteries. Indeed, these batteries would then be difficult to replace since they are located inside the tire.

[006] Therefore, other means have been sought to supply this electrical device. For example, it has been proposed to use the accelerations of the wheel caused, for example, by shocks or vibrations to produce electrical energy inside the tire to power the electrical device. This solution largely solves the power supply problems of the electrical device. However, when the motor vehicle is not used for a long time, the battery for starting the conversion of the acceleration into electrical energy is completely discharged. It is no longer possible to supply the electrical device. [007] The invention aims to solve this problem. It therefore relates to a wheel in which the device comprises a system for transforming the pressure difference between the confined gas under pressure inside the tire and the free air present outside the tire in electrical energy used to power the electrical device. [008] In the wheel above, it is the difference in pressure between the gas confined in the tire and the free air that is used to generate electrical energy. Thus, electrical energy can be generated even when the wheel is stationary and therefore even after a long period of no use of the motor vehicle. [009] Embodiments of this wheel may include one or more of the following features: B the system is equipped with:

An inlet nozzle fluidically connected to the pressurized gas and an outlet nozzle fluidically connected to the air present outside the tire,

At least one articulated arm displaceable under the action of the gas that expands when flowing from the inlet nozzle to the outlet nozzle, and An electromechanical transducer capable of converting the mechanical energy of movement of the arm into electrical energy used to power the sensor; B the wheel comprises a bottleneck adapted to limit the flow of gas flowing from the inlet nozzle to the outlet nozzle to less than 10 ^"5 m ³ / s or 10 ^" ⁶ m ³ / s;

B the outlet nozzle is fluidly connected to the outside air of the tire by a hole adapted to limit the flow of gas that escapes out to less than 10 ^"8 m ³ / s;

B the electronic device is a sensor of the pressure difference between the confined gas under pressure inside the tire and the free air present outside the tire;

B the transducer is capable of converting the mechanical energy of displacement of the arm into an electrical energy that can be used in addition as a physical quantity representative of the pressure difference; B the sensor comprises a wireless transmitter capable of transmitting a quantity representative of the pressure difference measured at a remote receiver via a wireless link, this transmitter being powered solely from the electrical energy produced by the system; B the system comprises at least two articulated arms between which flows the fluid to pass from the inlet nozzle to the outlet nozzle by moving these arms relative to each other, these arms being shaped and articulated from so that, during their movement, they define at least one fluid pocket which moves away from the inlet nozzle to then join the outlet nozzle while increasing volume at the same time; B the arms are shaped spirals nested one inside the other;

B the electrical device is a sensor of the pressure difference between the confined gas under pressure inside the tire and the free air present outside the tire and the transformation system is different from a microsystem equipped with two articulated arms between which flows the fluid to pass from the inlet nozzle to the outlet nozzle by moving these arms relative to each other, these arms being spirally shaped and articulated so that, during their movement, they define at least one fluid pocket that moves away from the inlet nozzle to then join the outlet nozzle while increasing volume at the same time. [ooio] These embodiments of the wheel further have the following advantages:

- use of a bottleneck which limits the flow of gas to less than 10 ^"5 m ³ / s prevents the wheel from deflating too quickly, - limiting the flow of gas to less than 10 ^"8 m ³ / s allows continuous production of electrical energy for more than 6 months while generating only negligible loss of pressure,

use in addition the quantity of electrical energy produced as a physical quantity representative of the pressure difference between the confined gas and the free air makes it possible to simply produce a sensor of this pressure difference,

- Powering a wireless transmitter from the electrical energy produced from the pressure difference makes it possible to obtain an autonomous pressure difference sensor, - Using articulated and articulated arms so that during their displacement, they define at least one gas flow pocket which moves away from the inlet nozzle and then rejoins the outlet nozzle makes it possible to transform the pressure difference into a mechanical displacement with a very good energy efficiency even for flow rates very low gas. In addition, it is not necessary to provide a nonreturn valve at the inlet nozzle.

The invention will be better understood on reading the description which follows, given solely by way of nonlimiting example and with reference to the drawings in which:

FIG. 1 is an illustration in partial section of a wheel incorporating an electrical device,

FIG. 2 is a more detailed schematic illustration of the electronic device of FIG. 1,

FIG. 3 is a schematic illustration of the device of FIG. 1 in the case where the latter is a pressure difference sensor, FIG. 4 is a schematic and sectional illustration of a valve of the wheel of the FIG. 1,

FIG. 5 is a schematic diagram of a microsystem for transforming a pressure difference in a fluid in mechanical displacement,

FIG. 6 is a graph showing the arm movement of the microsystem of FIG. 5 as a function of time,

FIG. 7 is a schematic illustration of the operation of the microsystem of FIG. 5,

FIG. 8 is a schematic illustration of a possible embodiment of the microsystem of FIG. 5, and FIG. 9 is a flowchart of a method of manufacturing the microsystem of FIG. 5,

FIGS. 10 to 12 are diagrammatic and cross-sectional illustrations of various steps in the manufacturing process of the microsystem of FIG. 5.

In these figures, the same references are used to designate the same elements. In the following description, the features and functions well known to those skilled in the art are not described in detail. FIG. 1 represents a wheel 110 equipped with:

a tire or tire 112 inside which compressed gas is confined, and an electrical device 100 requiring electric power to operate.

In the following description, it is considered that the compressed gas is the compressed air used to inflate the tire. However, other gases are usable to inflate the tire 112 such as nitrogen. The wheel 2 is for example the wheel of a motor vehicle such as a car.

The tire 112 is mounted on a rim 114. The device 100 is located inside the tire 112 which serves as a protective envelope.

Figure 2 shows in more detail the general architecture of the device 100.

The device 100 comprises a system 200 for transforming the pressure difference between the confined air under pressure inside the tire 112 and the free air present outside this tire with electrical energy. Free air is at atmospheric pressure. This electrical energy is used to power a set 202 of electrical components of the device 100.

The assembly 202 includes both electrical components that are necessary for the system 200 to operate as other electrical components necessary for the performance of the various functions that the device 100 must perform. For example, the assembly 202 comprises a wireless information transceiver as well as an electronic control unit.

The system 200 comprises: a transducer 204 capable of converting the pressure difference between the confined air and the free air into mechanical energy, and

a transducer 206 capable of converting this mechanical energy into electrical energy used to power the assembly 202.

The transducer 204 comprises an inlet nozzle 208 fluidly connected to the air confined inside the tire 112 and an outlet nozzle 210 fluidically connected to the open air.

At least one of the nozzles 208 or 210 forms a bottleneck 212 adapted to limit the flow of air through the transducer 204.

This neck 212 is shaped so that the air flow is very low, that is to say less than 100 mL / s, 10 mL / s or 1 mL / s. For example, here, the neck 212 is shaped to allow only an air flow rate of less than 100 .mu.l / s and, preferably, less than or equal to 10.

With such a flow rate of 100 μl / s, the leakage made through the tire 112 by the transducer 204 represents for a tire whose air volume is equal to 3.94 × 10 ^-2 m ³ a drop of pressure of 8 mBar after six months, which is negligible. Thus, the device 100 is able to operate for more than six months without forcing the owner of the vehicle to inflate the tire 112.

The transducer 204 comprises between the nozzles 208 and 210 at least one movable arm under the action of the air which expands flowing from the nozzle 208 to the nozzle 210.

In the particular case shown in Figure 2, the part that moves under the action of the air that relaxes is a turbine 216 formed of a central core 218 and several peripheral blades 220. Each blade 220 here corresponds to a movable arm. This turbine is rotated by the air flowing from the nozzle 208 to the nozzle 210.

To limit the size of the device 100, the system 200 is a microsystem. The microsystems are, for example, MEMS (Micro-ElectroMechanical Systems). These microsystems differ from macroscopic mechanical systems in addition to their manufacturing process. These microsystems are made using the same collective manufacturing processes as those used to make microelectronic chips. For example, microsystems are made from monocrystalline silicon wafer or machined glass by photolithography and etching (for example DRIE (Deep Reactive Ion Etching)) and / or structured by epitaxial growth and deposition of metallic material.

With these manufacturing processes, the microsystems are small and generally have parts or parts of machined parts of which at least one of the dimensions is of micrometric order. The micrometric order dimension is generally less than 200 μm and, for example, between 1 and 200 μm.

Implementations of the transducers 204 and 206 in the form of a microsystem are known.

For example, it is possible to refer to this subject in US Pat. No. 6,392,313 for an example of an embodiment of a microturbine capable of relaxing a compressed gas and a transducer associated with this microturbine for transform the rotation of the microturbine into electrical energy. For example, the microsystem 200 is identical to that described in US Pat. No. 6,392,313 except that the gas under pressure does not result from the combustion of a fuel mixture but corresponds to the pressurized air under pressure. 112. Thus, all the elements of the micromotor described in US application 6 392 313 and used to compress a gas can be omitted. For example, with reference to FIG. 1 of US Pat. No. 6,392,313, the microcompressor (disc 18, blade 20 ...), the fuel injector 24, the combustion microchamber 30, etc. can be omitted. . Here, the turbine 216 is identical to that described with reference to Figure 1 of US Patent 6,392,313 (valve 34, disc 36, blade 38, shaft 40, ...). An embodiment of the transducer 206 is for example described with reference to Figure 6 of US Patent 6,392,313.

Many other embodiments of the transducers 204 and 206 are possible. In particular, embodiments of embodiments with a single oscillating arm are described, for example, in the patent applications WO 03 05 6691 and

WO 2006/095039.

A particular embodiment of the transducers 204 and 206 is also described below with reference to FIGS. 5 to 8.

Figure 3 shows the device 100 in the particular case where it is a sensor of the pressure difference between the confined air under pressure inside the tire 112 and the air outside the outside of this tire.

For this, the device 100 exploits the fact that the pressure difference between the nozzles 208 and 210 is a function, for example proportional, to the mechanical energy produced by the movements of the arm or the transducer 204. In addition, since the electrical energy produced by the transducer 206 is a function of the mechanical energy received, this electrical energy is also a function of the pressure difference between the nozzles 208 and 210. It is this property of the system

200 which is used to realize a sensor of the pressure difference.

For this purpose, in FIG. 3, the assembly 202 comprises: a device 26 for storing the electrical energy generated by the system 200, such as a capacitor,

a unit 28 for controlling the system 200,

a circuit 102 for managing the charging and discharging of the device 26, and

- A radio transmitter 104 capable of communicating information representative of the pressure difference between the nozzles 208 and 210 to a remote radio receiver.

For example, the device 100 triggers the sending of a characteristic signal via the transmitter 104 as soon as the load of the device 26 exceeds a predetermined threshold FL Thus, the time that elapses between two transmissions is a function, for example proportional, to the measured pressure difference. It is therefore possible from the data received to deduce the difference in pressure between the nozzles 208 and 210.

Here, the only Fi is fixed so as to allow the supply of the assembly 202 and in particular of the transmitter 104 so that it emits a characteristic pulse. Thus, in this embodiment, the device 100 does not need other external power sources to operate. Indeed, it uses only as a source of energy the pressure difference that exists between the nozzles 208 and 210. Under these conditions, it is said that the device 100 is autonomous in energy since it does not need to other sources of energy than that extracted from the pressure difference. Figure 4 shows a possible example of mounting the device 100 inside the tire 112. More specifically, the tire 112 has a valve 116 through which the wheel 110 can be inflated. Conventionally, this valve consists of a barrel 118 fixed without any degree of freedom to the tire 112 and a movable valve 120. This valve 120 is movable between a rest position in which it hermetically seals the tire and an active position in which it allows the introduction of compressed air inside the tire 112. Here, a hole 124 is hollowed through the valve 120 to allow the passage of the nozzle 210 through the valve 120 and thus the connect to outside air.

In this embodiment, the device 100 is fixed without any degree of freedom to the valve 120. Thus, when the valve 120 is in its rest position, the compressed air leaks through the device 100 and the hole 124. The flow rate of the air leak is very low, that is to say less than 1 mL / s. For example, here, the hole 124 is dimensioned so as to allow air leakage only less than 100 .mu.l / s and, preferably, less than or equal to 10 .mu.l / s. FIG. 5 represents a particular case of a microsystem 2 for transforming a pressure difference in a fluid in mechanical displacement. This microsystem 2 can be used as a system 200 in the embodiments described with reference to FIGS. 1 to 4. The microsystem 2 comprises a closed enclosure 4 fluidically connected to the compressed fluid via an inlet nozzle 6 and fluidically connected to the expanded fluid via an outlet nozzle 8. The enclosure 4 is hermetically sealed so that the fluid expanded in this enclosure can not escape through Other outlets than the nozzle 8. Inside the enclosure 4, the nozzle 6 is fluidly connected to a roller expander 10. The roller expander is also known as the "Scroll" expander.

The expander 10 is formed of two arms articulated with respect to each other 12 and 14. The arms 12 and 14 are shaped and articulated so that during their movement under the effect of the fluid admitted by the nozzle 6, they define at least one fluid pocket which moves away from the nozzle 6 to then approach the nozzle 8 while increasing volume. For example, the arms 12 and 14 are spiral shaped and nested within each other. Each spiral has at least one turn or several turns to define several fluid pockets that move at the same time from the nozzle 6 to the nozzle 8. Each arm is mechanically connected via respective hinges 16 and 18 to a plane fixed 20 (Figure 8). To simplify FIG. 5, only anchor points 21 at plane 20 are shown in this figure. The plane 20 extends parallel to orthogonal X and Y directions. Preferably, the joints 16 and 18 are elastic.

The joints 16 and 18 allow only a translational movement of the arms 12 and 14 along, respectively, Y and X directions.

Each arm 12, 14 is also mechanically connected to a respective electromechanical transducer 22, 24. Each electromechanical transducer is adapted to convert the mechanical movement of the arm into electrical energy. For example, each of these transducers 22, 24 is connected at the output to an electrical energy storage device such as the device 26 (Figure 3). Transducers 22 and 24 are electromechanical transducers controllable so as to adjust the amount of mechanical energy converted into electrical energy. They therefore also fulfill the function of controllable damper.

These transducers 22 and 24 are controlled by a control unit such as the unit 28 (Figure 3). The unit 28 is here connected to sensors 30 and 32 of a physical quantity representative of the electrical power produced, respectively, by the transducers 24 and 22. The sensors 30 and 32 also make it possible to measure the phase of the electrical power produced. .

A mechanical phase shifter 36 is mechanically connected between the arms 12 and 14. This function of the phase shifter is to help mechanically to achieve a phase shift of ττ / 2 radians between the movements of oscillations (back and forth ) In addition, this phase shifter 36 is formed by a spring 38 mechanically connected to the arms 12 and 14. For example, this spring 38 is a spring blade. This spring 38 transforms the system formed by the two arms 12 and 14 and the spring 38 into a resonant system for a resonance frequency. The resonance frequency is reached when the phase difference between the oscillations movements of the arms 12, 14 is ττ / 2 radians. At the resonant frequency, the energy efficiency of the microsystem is maximal.

The unit 28 is able to control the transducers 22 and 24 to work at the resonant frequency. For example, on the basis of the information measured by the sensors 30 and 32, the unit 28 calculates the phase difference between the oscillation movements of the arms 12 and 14 and locks this phase shift on the value ττ / 2. To limit the energy consumed by the microsystem 2 during its operation, the unit 28 is itself powered from the electrical energy produced by the transducers 22 and 24. For this purpose, for example, the unit 28 is electrically connected to the device 26 for storing electrical energy. FIG. 6 represents the evolution over time of displacements of the arms 12 and 14, respectively, along the directions Y and X. More specifically, the curves 44 and 46 represent the displacements, respectively, of the arms 12 and 14. These displacements are sinusoidal and out of phase with respect to each other by ττ / 2 radians.

In steady state, each arm describes a movement of oscillations or back and forth between two extreme positions noted X _ma χ and X _mn for the arm 14 and Y _max and Ymin for the arm 12 in Figure 2 .

The displacement of the arms 12, 14 defines a plurality of fluid pockets that moves circularly from the nozzle 6 to the nozzle 8 by increasing volume. Specifically, each fluid pocket moves around and at the same time away from the nozzle 6.

FIG. 7 shows in more detail the displacement of a pocket 50 of fluid from the nozzle 6 towards the nozzle 8.

Initially (state I), the pocket 50 is in fluid communication with the nozzle 6. This pocket 50 is filled with compressed fluid. Then (state II), the arms 12 and 14 move relative to one another to fluidly isolate this pocket 50 from the nozzle 6.

Then, as shown by the successive states (state III in state Vl), the pocket 50 moves from the nozzle 6 to the nozzle 8 by describing a spiral movement around the nozzle 6. More precisely, after the arms 12 and 14 have each performed a complete back and forth, the pocket 50 has moved from the position shown in the state I to the position 52 represented in the state I. It has therefore performed a complete turn around the nozzle 6.

Here, since the arms 12 and 14 in the form of a spiral are wound several times around the nozzle 6, during the next cycle of oscillations of the arms 12 and 14, the pocket 50 makes a new turn around the nozzle 6 but moving away a little more from it. More precisely, after a complete new turn, the pocket 50 occupies the position 54 (state I). Finally, during his last turn, the pocket 50 occupies the position 56 (state I). In the state 56, the bag is in fluid communication with the nozzle 8, allowing the expanded fluid to escape. Here, the arms 12 and 14 are shaped to simultaneously define at least two pockets that move at the same time from the nozzle 6 to the nozzle 8 by increasing volume. In the particular case shown in Figure 7, the arms 12 and 14 are shaped to define six fluid pockets that move simultaneously from the nozzle 6 to the nozzle 8. [0065] It is therefore understood that when the fluid expands in the Expander 10, the energy of this trigger is converted into a mechanical movement of the arms 12 and 14. In the particular case shown in Figure 5, this mechanical displacement is converted by the transducers 22 and 24 into electrical energy. FIG. 8 represents an example of possible implementation of the microsystem 2. For example, the hinge 16 and the transducer 22 are identical, in the near position, the hinge 18 and the transducer 24. Thus, only the hinge 16 and the transducer 22 are described here in more detail.

The hinge 16 is here made using a parallelogram 60 fixed without any degree of freedom to the arm 12. This parallelogram 60 thus moves in translation along the Y direction parallel to the plane 20. The parallelogram 60 is mechanically connected to the plane 20 via beams 62. Each beam 62 has a fixed end without any degree of freedom to the parallelogram 60 and another end fixed to the anchor point 21 itself fixed without any degree of freedom in the plane 20. The beam 62 is not directly fixed to the plane 20. Preferably, each beam 62 is extending parallel to the direction X. In addition, each beam 62 is thin enough to be twisted when the fluid is relaxes in the pockets defined between the arms 12 and 14. With this configuration, the arm 12 can only move along the Y direction. [0069] The transducer 22 uses for example a capacitor with variable capacitance. iable to transform the mechanical energy produced by the movement of the arm 12 into electrical energy. The conversion of mechanical energy into electrical energy using variable capacitors is well known. For example, this is used in patent applications WO2007 082 894 and FR2 897 486. Thus, this conversion mechanism will not be described in detail. Here, the capacitor is made using interdigitated combs. More specifically, an armature 66 of the capacitor is fixed without any degree of freedom to the parallelogram 60. The other armature 68 of this capacitor is fixed without any degree of freedom on the plane 20. Thus, when the parallelogram 60 moves, it modifies the capacity of the capacitor, which is then used to transform mechanical energy into electrical energy. Preferably, at least one of the capacitor plates comprises electrets. Indeed, this allows the transducer 22 to begin to produce electrical energy without prior input of electrical energy from a source of external electrical energy. An exemplary method of manufacturing the microsystem 2 will now be described with reference to the method of Figure 9 and with the aid of the illustrations of Figures 10 to 12.

Initially, during a step 80, a plate comprising a sacrificial intermediate layer 82 is etched. Typically, this plate is a SOI (Silicone On Insulator) plate. Thus, this plate comprises in addition to the sacrificial layer 82 on one side a silicon layer 84 and on the other side a layer of insulator 86. In step 80, the spirals, the joints and the capacitor to variable capacitance are etched in the layer 84. In FIG. 10, the microsystem thus etched is represented by a block 90. The block 90 rests on the layer 82. Then, during a step 92, the layer 82 is removed below the block 90. For example, etching is used to remove the sacrificial layer. From this moment, the spirals 12 and 14 and the parallelograms of the joints as well as the armatures 66 of the capacitors with variable capacity can move in translation relative to the plane 20 constituted by the upper face of the layer 86 (see FIG. 11) .

Then, during a step 94, a cover 96 is made and this cover is assembled above the layer 84. For example, the cover 96 is made of glass. The nozzles 6 and 8 are made in this cover 96. Only the nozzle 6 has been shown in FIG. 12.

Access holes to the layer 84 are also made in the cover 96 for electrically connecting the transducers 22 and 24 to the control unit 28 and the energy storage device 26. In Figure 12, only one hole 98 for access to layer 84 has been shown. Note that the thickness of the layer 82 and the space between the cap 96 and the block 90 have been exaggerated in Figures 10 to 12. In practice, the thickness of the layer 82 and the space between the cover 96 and the block 90 are sufficiently reduced so that the fluid that expands in the expander 10 remains confined between the arms 12 and 14. [0076] Many other embodiments are possible. For example, the device 100 need not be autonomous. It can also use electrical energy produced by other energy sources such as a non-contact rechargeable battery using a device outside the wheel. In another embodiment, the system 200 is combined with another system for producing electrical energy such as a system capable of transforming accelerations experienced by the wheel into electrical energy.

The system 200 is not necessarily a microsystem. Alternatively, it is a macroscopic system. The electrical device is not necessarily a sensor of the pressure difference. For example, it may be a tire adhesion sensor 112 on the road or a temperature sensor. The electrical device is not necessarily a sensor either. For example, the assembly 202 may include a light or other indicator so as to allow the supply of this indicator light from the pressure difference between the air confined inside the tire and the open air.

The arms 12 and 14 may be mechanically prestressed so that, whatever the position of these arms, there is always at least one elastic hinge which has a non-zero elongation, that is to say that it is is not at his rest position. Many different spiral shapes are possible for the arms

12 and 14. For example, it may be a volute or an Archimedean spiral.

Each arm may have one or more spirals.

It is not necessary that the arms 12 and 14 are mounted in translation along perpendicular axes. In fact, it is sufficient that the axes along which the arms 12 and 14 move are non-parallel. If the angle between these axes is different from ττ / 2 radians, then the phase shift between the oscillation movements of the arms 12 and 14 must be adapted accordingly.

It is also not necessary for the arms 12 and 14 to work at the resonance frequency.

In a simplified embodiment, the mechanical phase shifter 36 may be omitted. In this case, the predetermined phase shift between the movements of the arms can be provided by an electric actuator such as for example an electromechanical transducer. The mechanical phase shifter can also be achieved without resorting to a spring. For example, it can be achieved using a connecting rod mechanism and crank.

For the transformation of a pressure difference into a mechanical displacement, the conversion of the mechanical energy thus produced into electrical energy is optional. Indeed, for the system 2 to work, it suffices to have controllable dampers enabling the movements of the arms 12 to be enslaved and

14 to maintain the appropriate phase shift.

Many other methods of manufacturing the microsystem 2 are possible.

In particular, the etching steps can be replaced by deposition steps.

Claims

1. Wheel equipped with a tire (1 12) and an electrical device (100) requiring to be powered to operate, characterized in that the device comprises a system (200; 2) for transforming the pressure difference. between a confined gas under pressure inside the tire and the free air present outside the tire in electrical energy used to power the electrical device.

Wheel according to claim 1, wherein the system (200; 2) is equipped with:

An inlet nozzle (208; 6) fluidically connected to the pressurized gas and an outlet nozzle (210; 8) fluidically connected to the air present on the outside of the tire; at least one hinged arm (220; 12,14) displaceable under the action of the gas which expands when flowing from the inlet nozzle to the outlet nozzle, and

An electromechanical transducer (206; 22; 24) capable of converting the mechanical energy of displacement of the arm into electrical energy used to power the sensor.

3. Wheel according to claim 2, wherein the wheel comprises a throttle neck (212; 124) capable of limiting the flow rate of the gas flowing from the inlet nozzle to the outlet nozzle within 10 ^{". 5} m ³ / s or 10 ^"6 m ³ / s.

4. Wheel according to claim 3, wherein the outlet nozzle (210; 8) is fluidly connected to the outside air outside the tire by a hole (124) able to limit the flow of the gas that escapes. outward to less than 10- ⁸ m ³ / s.

5. Wheel according to any one of the preceding claims, wherein the electronic device (100) is a sensor of the pressure difference between the confined gas under pressure inside the tire and the free air present outside. of the tire.

6. Wheel according to claim 5, wherein the transducer (206; 22; 24) is adapted to convert the mechanical energy of movement of the arm into a usable electrical energy additionally as a physical quantity representative of the pressure difference.

The wheel according to claim 5 or 6, wherein the device comprises a wireless transmitter (104) capable of transmitting a magnitude representative of the measured pressure difference to a remote receiver via a wireless link, this transmitter being fed only from the electrical energy produced by the system (2).

8. Wheel according to any one of the preceding claims, wherein the system comprises at least two articulated arms (12, 14) between which flows the fluid to pass from the nozzle (6) to the inlet nozzle (8). ) by moving said arms relative to one another, said arms (12, 14) being shaped and articulated so that, during their movement, they define at least one pocket (50) of fluid that moves away from the inlet nozzle to then join the outlet nozzle while increasing volume at the same time.

9. Wheel according to claim 8, wherein the arms (12, 14) are shaped spirals interlocked into one another.

Wheel according to any one of claims 1 to 7, in which the electrical device (100) is a sensor of the pressure difference between the gas confined under pressure inside the tire and the free air present at the vehicle. tire outside and the transformation system is different from a microsystem equipped with two articulated arms (12, 14) between which flows the gas to pass from the inlet nozzle to the outlet nozzle by moving these arms relative to each other, said arms (12, 14) being spirally shaped and articulated so that, during their movement, they define at least one pocket (50) of gas which moves away from the inlet nozzle to then join the outlet nozzle while at the same time increasing volume.