Vehicle wheel comprising a drive device and a braking device

Abstract

Disclosed is a vehicle wheel (1) rotatably mounted on an axle (E) and comprising: - an annular rim (2), a web (3) and a hub (4) delimiting a closed-off annular space, - an electric motor (10) comprising a first stator (11) and a first rotor (12) which are arranged coaxially to the wheel, and - a magnetic brake (20). The motor and the brake extend one inside the other within the annular space. Either the first rotor serves as a rotor for the brake (22), or the first stator (11) serves as a stator for the brake (21) in order to produce a second magnetic flux capable of inducing eddy currents that generate a braking torque. Either the first stator or the first rotor has a Halbach array formed at least in part by electromagnets.

Description

[0001]VEHICLE WHEEL COMPRISING A DRIVE DEVICE AND A BRAKING DEVICE The present invention relates to the braking and ground movement of a vehicle and, more particularly, to a wheel comprising a braking device and a drive device. BACKGROUND OF THE INVENTION In the field of aviation, it is now planned to equip aircraft wheels with rotational drive members to enable aircraft to move on the ground without using their powertrains. It is also known to equip aircraft wheels with a brake intended to selectively slow down and stop said aircraft when they are moving on the ground. The brake is generally friction-based so that it requires the replacement of wear elements whose friction, during braking, generates particularly polluting dust particles.However, in the case of electric vertical take-off and landing (eVTOL) aircraft, the wheels are traditionally small (between 6 and 10 inches), making it very difficult to integrate both a drive and a brake. Furthermore, the landing gear of eVTOL aircraft is generally fixed, i.e., not movable between a retracted and a deployed position as is the case for larger aircraft. Increasing the size of the wheels to integrate a drive and a brake would therefore tend to increase the drag forces exerted on the landing gear during flight, and therefore reduce the flight range of the eVTOL. However, climate change is a major concern for many legislative and regulatory bodies around the world.Indeed, various carbon emission restrictions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new aircraft types and those currently in operation, requiring the implementation of technological solutions to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to contribute to the fight against climate change. Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. All stakeholders in the sector are constantly working to improve energy efficiency.The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of air transport. Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible to reduce the environmental footprint of its activity.This sustained research and development work relates to new generations of aircraft engines, the lightening of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, essential complements to technological progress, aeronautical biofuels. OBJECT OF THE INVENTION The invention aims to propose a wheel integrating a drive device and a braking device making it possible to at least partially overcome the aforementioned drawbacks.SUMMARY OF THE INVENTION To this end, according to the invention, a vehicle wheel is provided, rotatably mounted on an axle, comprising: − an annular rim connected by a disc to a hub pivotally received on the axle, the rim delimiting with the hub an annular space closed by the disc; − a radial flux electric motor comprising a first stator and a first rotor arranged coaxially with the wheel to produce between them a first magnetic flux capable of generating a torque for driving the wheel in rotation; − a magnetic brake.According to the invention, the electric motor and the magnetic brake extend into each other inside the annular space, the first rotor also serving as a rotor for the magnetic brake so as to produce with a stator of the magnetic brake a second magnetic flux capable of generating eddy currents generating a braking torque of the wheel, the stator of the magnetic brake being arranged coaxially with the wheel, or the first stator also serving as a stator for the magnetic brake so as to produce with a rotor of the magnetic brake a second magnetic flux capable of generating eddy currents generating a braking torque of the wheel, the rotor of the magnetic brake being arranged coaxially with the wheel.This results in a radial superposition of the electric motor and the magnetic brake and even a partial fusion of the electric motor and the magnetic brake since the first rotor or the first stator of the electric motor also serves as an active element for the magnetic brake. The electric motor and the magnetic brake are engaged with each other and occupy a relatively small volume. This allows the integration of the electric motor and the magnetic brake inside the wheel without significantly increasing the drag forces which oppose the movement of said wheel. The invention thus makes it possible to associate with an aircraft wheel both an electric motor and a magnetic brake even if the wheel is small. The mass of the assembly formed by the electric motor and the magnetic brake is thus relatively low. Furthermore, ground maintenance operations are thus simplified.It is advantageously noted that with the invention it is not necessary to provide the wheel with an actuation system making it possible to switch from the function of the electric motor to that of the magnetic brake. Optionally, one of the first or second rotor is adjacent to the rim and the other of the first rotor and the second rotor is adjacent to the hub, the first stator and the second stator extending between the first rotor and the second rotor. Optionally, the first stator and the second stator are radially opposite each other. Optionally, the first stator extends inside the second stator. Optionally, the first stator or the first rotor comprises a Halbach network formed at least in part by electromagnets, that of the first stator or the first rotor comprising the Halbach network being that also serving as stator, respectively rotor, for the magnetic brake.Optionally, the first rotor comprises permanent magnets and / or electromagnets capable of interacting with the electromagnets equipping the first stator. Optionally, the Halbach network is formed by a succession of electromagnets extending circumferentially around the hub and / or extending axially along the hub. Optionally, the magnetic brake is radial flux. Optionally, the first stator is fixed to a support immobile with respect to the axle. Optionally, the second rotor is formed by the rim made of electrically conductive material or is formed by a local coating arranged on an internal periphery of said rim, the coating being made of electrically conductive material. The invention also relates to an aircraft landing gear comprising at least one wheel as mentioned above. The invention also relates to an aircraft comprising at least one landing gear as mentioned above.BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood in light of the following description, which is purely illustrative and non-limiting, and must be read in conjunction with the appended drawings, among which: [Fig. 1] Figure 1 is a simplified representation of an aircraft comprising main landing gears each provided with a wheel according to the invention; [Fig. 2] Figure 2 is an axial sectional view of one of the wheels of the aircraft illustrated in Figure 1, according to a first embodiment of the invention; [Fig. 3] Figure 3 is a schematic diagram of the arrangement according to a cross-section of the wheel illustrated in Figure 2; [Fig. 4] Figure 4 is a schematic diagram illustrating how a magnetic flux can drive or brake the wheel illustrated in Figure 2; [Fig.5] Figure 5 is an axial sectional view of one of the wheels of the aircraft illustrated in Figure 1, according to a second embodiment of the invention.DETAILED DESCRIPTION OF THE INVENTION With reference to Figure 1, the invention is described in application to an electric vertical takeoff and landing (eVTOL) aircraft A. To fly, land and take off, the aircraft A is equipped with at least one powertrain M. The aircraft A comprises two main landing gears P, each comprising a leg J ​​having an upper end fixed to a structure S of the aircraft and, opposite, a lower end carrying a wheel 1 rotating about an axis X on an axle E. The landing gears P are fixed here, but the invention is applicable to retractable type landing gears, or even to another type of aircraft or to another type of vehicle such as a land vehicle. According to a first embodiment, illustrated in Figure 2, the wheel 1 comprises an annular rim 2 connected by a web 3 to a hub 4 pivotally received on the axle E by means of bearings 5, 6.The rim 2 extends coaxially around the hub 4 and delimits with said hub 4 an annular space having one end at least partially closed by the web 3 and, opposite, an open end. The rim 2 and the hub 4 thus extend coaxially with the axis X. The wheel 1 is said to be “motorized”, that is to say equipped with a drive device intended to move the aircraft A without using its powertrains when the latter is on the ground. The drive device comprises a radial flux electric motor 10 comprising, in a manner known per se, a first fixed element or stator 11, and a first rotating element or rotor 12. The stator 11 and the rotor 12 each have a central axis coincident with the axis X (which is therefore the axis of rotation of the wheel 1). The stator 11 and the rotor 12 thus extend coaxially to the axis X. The stator 11 and the rotor 12 thus extend coaxially to the rim 2 and the hub 4.Furthermore, the rotor 12 extends radially opposite the stator 11. Optionally, the rotor 12 extends inside the stator 11. The wheel also has a support 30 secured to the axle E. The support is for example shaped as a plate. The support extends for example coaxially to the hub 4. Optionally, the stator 11 is fixedly mounted on the support 30. The stator 11 is thus immobile with respect to the support 30 and therefore immobile with respect to the axle E. The stator 11 here has the shape of a crown. The stator 11 thus has an external circumferential face (forming an external main surface 11.1), an internal circumferential face (forming an internal main surface 11.2), a first lateral flank connecting the two circumferential faces and a second lateral flank (opposite the first lateral flank and optionally parallel to the first lateral flank) connecting the other two circumferential faces.The first lateral flank is the one fixed to the flat support 30. The second lateral flank is opposite the disc 3. The main surface 11.1 is opposite the rim 2. The main surface 11.2 is opposite the rotor 12. The rotor 12 here has the shape of a crown. The rotor 12 is here fixedly mounted on the disc 3, so that said rotor 12 is immobile with respect to the wheel 1. The rotor 12 comprises a series of permanent magnets (not shown). The permanent magnets are for example arranged so as to have an alternation of north poles and south poles on the same main surface 12.1 of the rotor 12, a surface which is opposite the main surface 11.2 of the stator 11. The wheel 1 is also said to be “braked”, that is to say equipped with a braking device intended to selectively slow down the aircraft A when it is on the ground.The braking device comprises a radial flux magnetic brake 20 and comprises, in a manner known per se, a second fixed element or stator 21, and a second rotating element or rotor 22. The stator 21 and the rotor 22 each have a central axis coincident with the axis X of rotation of the wheel 1. The stator 21 and the rotor 22 extend coaxially with the hub 4. The stator 21 is here formed directly by the stator 11 of the electric motor 10. Hereinafter, only the stator 11 will be referred to, which is therefore also the stator 21. The stator 11 and the rotor 22 extend radially opposite each other. In the present case, the stator 11 extends inside the rotor 22. The stator 11 comprises a series of electromagnets (not shown). The electromagnets are arranged to form a Halbach network.It is recalled for the present application that a Halbach array is a particular arrangement of aligned permanent magnets, which increases the magnetic field on one side of the alignment while almost completely eliminating the magnetic field on the other side of the alignment. This is obtained by rotating the orientations of the magnetic fields on the successive magnets of the alignment (for the same surface of the alignment the arrangement of the permanent magnets is thus as follows: north pole on the left, north pole upwards, north pole on the right and north pole downwards; north pole on the left, north pole upwards, north pole on the right and north pole downwards, etc.). In the present case, thanks to the arrangement of the stator 11, the electromagnets form both the main external surface 11.1 of the stator 11 and the main internal surface 11.2 of the stator 11. As shown schematically in Figure 3, on the main surface 11.1 of the stator 11, the electromagnets are arranged so as to find successively in the circumferential direction: - a north electromagnet 31 (i.e. the north pole of the electromagnet 31 is opposite the rotor 22 – we can thus deduce that the south pole of this same electromagnet 31 is opposite the rotor 12), - an east electromagnet 32 ​​(i.e. the north pole of the electromagnet 32 ​​is oriented to the right of the north pole of the north electromagnet 31), - a south electromagnet 33 (i.e. the north pole of the electromagnet 33 is opposite the rotor 12 – we can thus deduce that the south pole of this same electromagnet 33 is opposite the rotor 22), - a west electromagnet 34 (i.e. the north pole of the electromagnet 34 is oriented to the left of the north pole of the electromagnet 31), this succession of four electromagnets continuing all around the stator 11. The rotor 22 is here formed directly by the rim 2.The rim 2 is for example made of an electrically conductive material (for example aluminum, steel, etc.). The rim 2 comprises an internal periphery defining a main surface 22.1 of the rotor 22 which is separated from the main surface 11.1 of the stator 11 by a predetermined air gap e. It is therefore understood that the rotor 22 is stationary with respect to the wheel 1. It is thus noted that the same stator is used both for the electric motor 10 and for the braking device 20: in service depending on the direction of circulation of the current passing through the electromagnets, the stator 11 can in fact be used to drive the wheel 1 in rotation or to brake the same wheel 1. It is understood that the air gaps between the stator 11 and the rotor 22 on the one hand and between the stator 11 and the rotor 12 must remain small so that the electric motor 10 as well as the braking device 20 can operate efficiently.As the rotor 22 is formed by the rim 2, it imposes here the positioning of the stator 11 (with respect to the air gap e) which therefore itself imposes the positioning of the rotor 12 (with respect to the air gap e' existing between the rotor 12 and the stator 11). Thus the rotor 12 is fixed to the disc 3 at a predetermined distance from the axis X. It is noted in the present case that the rotor 12 is closer to the stator 11 than to the axle E. The rotor 12 therefore delimits with the axle E an internal sub-volume which can accommodate one or more other elements (reduction box, sensor, etc.). The permanent magnets of the rotor 12 are therefore able to interact with the electromagnets equipping the stator 11 to produce a first magnetic flux driving the rotor 12, and therefore the wheel 1, in rotation around the axis X.Indeed, when the electromagnets equipping the stator 11 are crossed by an electric current in a first direction of circulation, they generate magnetic fields sufficient to generate a driving torque in rotation of the hub 4, and therefore of the wheel 1, by interacting with the series of permanent magnets equipping the rotor 12. Furthermore, the electromagnets of the stator 11 are arranged so as to produce a second magnetic flux generating eddy currents in the rim 2 when said electromagnets are crossed by an electric current in a second direction of circulation (opposite to the first direction of circulation) and the wheel 1 rotates around its axis X of rotation. Indeed, when the electromagnets equipping the stator 11 are crossed by an electric current, they generate in the rotor 22 eddy currents sufficient to generate a braking torque on said rotor 22, and therefore the wheel 1.With reference to Figure 4, the electromagnets of the stator 11 forming a Halbach network are thus arranged so as to: - for the first direction of current flow, maximize the portion of the first magnetic flux 23 seen by the electric motor 10 and to limit as much as possible (or even eliminate) the portion of the first magnetic flux sent to the rim; - for the second direction of current flow, maximize the portion of the second magnetic flux 24 seen by the rim 2 and to limit as much as possible (or even eliminate) the portion of the second magnetic flux sent to the electric motor 10. Preferably, the stator 11 is configured so that for the second direction of current flow, the Halbach network is fixed in position, that is to say that the different poles of the electromagnets are not swapped when the magnetic brake 20 is used.Thus, during braking, only the magnitude of the second magnetic flux can vary (depending on the intensity of the electric current flowing through the stator 11). Preferably, the stator 11 is configured so that for the first direction of current flow, the Halbach network is not fixed in position. Preferably, only the east and west electromagnets (by being placed at the main surface 11.2 of the stator 11) remain fixed in position when the electric motor 10 is used. On the other hand, the north and south electromagnets (by being placed at the main surface 11.2 of the stator 11) are electronically controlled so that they can be swapped into south and north electromagnets respectively at regular intervals. Thus, not only can the magnitude of the first magnetic flux vary (depending on the intensity of the electric current flowing through the stator 11) but its direction as well.It is thus possible to cause a relative rotational movement between the rotor 12 and the stator 11 by controlling the north and south electromagnets. The electric motor 10 and the magnetic brake 20 thus work independently of each other but using common elements. This makes the electric motor 10 and magnetic brake 20 assembly particularly compact and lightweight. In particular, the electric motor 10 and the magnetic brake 20 extend entirely within the annular space defined by the wheel 1. It will also be noted that using the rim 2 as a heat sink and eddy current conductor jointly contributes to making this assembly more compact and lighter. In addition, because the electric motor 10 and the magnetic brake 20 extend entirely within the annular space defined by the wheel 1, the drag forces exerted on the undercarriage P are limited, especially since said undercarriage P is not retractable here.Such an arrangement of the electric motor 10 and the magnetic brake 20 thus limits the aerodynamic impact of the landing gear P. It will also be noted that such an arrangement of the electric motor 10 and the magnetic brake 20 makes it possible to simplify the integration of a drive device and a braking device while maintaining adequate performance. With reference to FIG. 5, a second embodiment will now be described. The second embodiment is identical to the first embodiment except that the rotor 12 is not fixedly mounted to the web 3 but is fixedly mounted on an external periphery 36 of the hub 4. The external periphery 36 of the hub 4 extends coaxially to the axle E and / or to the axis X. The external periphery 36 of the hub 4 thus extends radially opposite the rotor 12. It is therefore understood that the rotor 12 is stationary with respect to the wheel 1.In order to comply with air gap values ​​e and e' that are sufficiently low for the braking device and the motor 10 to operate correctly, the rotor 12 may be directly fixed to the hub 4 or may be fixed to the hub 4 by means of an additional part 37. Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims. The wheel 1 may have a structure different from that described. The rim 2 of the wheel 1 may, for example, be formed of two half-rims, be made in a single piece, made in a foundry or by additive manufacturing, etc. Materials other than those indicated may be used. Although the rim 2 here forms the rotor 22 of the magnetic brake 20, it may also have its internal periphery provided with a local coating capable of forming said rotor 22 (for example, made of copper, aluminum, silver, nickel, etc.).The rim 2 can then be made of a material different from that of the covering. The stator 11 may not be mounted fixed to the axle E (directly or via a support) but be mounted fixed to another part of the aircraft such as to one of its landing gears (either directly or via a support). The arrangement of the electric motor 10 and the magnetic brake 20 can be reversed. In other words, the stator 11 and the rotor 12 of the electric motor 10 can respectively take the place of the stator 21 and the rotor 22 of the magnetic brake 20, and vice versa. The permanent magnets can be carried by the stator 11 instead of the rotor 12. The electromagnets can be carried by the rotor 22 instead of the stator 21. It is therefore understood that it is the rotors 12 and 22 of the electric motor 10 and the braking device 20 respectively which are then merged and the stators 11 and 21 which are distinct.The drive device may further comprise a reducer to increase the drive torque delivered to the wheel 1 by the electric motor 10. The reducer may be of any type: planetary reducer, strain wave reducer, cycloidal reducer, etc. Such a reducer may thus be arranged between the rotor 12 and the wheel 1. For example, the rotor 12 may be fixedly mounted to the reducer which will itself be fixedly mounted to the disc 3 and / or to the hub 4. For example, the reducer may thus be the additional part 37 shown in FIG. 5. Although the rotor 12 of the electric motor 10 here comprises only permanent magnets to, for example, form a synchronous motor, it may also comprise electromagnets to, for example, form an asynchronous motor.Whether the rotor 12 carries electromagnets and / or permanent magnets, said electromagnets and / or said permanent magnets may optionally be arranged so as to form or not a Halbach network. Although the stator 21 of the magnetic brake 20 here comprises only electromagnets, it may also comprise permanent magnets. In particular, the electromagnets and the permanent magnets of the magnetic brake 20 may be arranged so as to form a Halbach network such that (for the main surfaces of the stator 21) the permanent magnets have an alternation of north poles and south poles, and the electromagnets have an alternation of east poles and west poles, with a magnet succeeding an electromagnet in at least one circumferential direction and / or an axial direction.Although the rotor 22 of the magnetic brake 20 is here formed by the rim 2 or by a local coating arranged on the internal periphery of said rim 2, it can also be formed by any element attached directly or indirectly to the rim 2. The arrangement and the number of bearings 5, 6 making it possible to ensure the rotation of the wheel 1 around the axis X can be different from those described and illustrated. At least one bearing can be arranged between the rim 2 and the support 30 and / or the stator 11. For example, at least one bearing can be arranged between the rim 2 and the support 30 and / or the stator 11 so as to guarantee a constant air gap e between the main surface 11.1 of the stator 11 and the main surface 22.1 of the rotor 22 so that the braking torque exerted by the magnetic brake 20 is constant (the braking torque being, in a manner known per se, a function of the air gap e). At least one bearing may be arranged between the stator 11 and the rotor 12.For example, at least one bearing may be arranged between the stator 11 and the rotor 12 so as to guarantee a constant air gap e' between the main surface 11.2 of the stator 11 and the main surface 12.1 of the rotor 12 so that the torque exerted by the electric motor 10 is constant (the torque being, in a manner known per se, a function of the air gap e'). The number of stators (11, 21) and / or rotors (12, 22) may be different from those described. The invention is applicable to other types of eddy current brake, in particular axial flux or combining axial flux with radial flux. The invention can be used on any type of vehicle, aerial (aircraft, airplane, helicopter, UAM, eVTOL, etc.) or terrestrial or amphibious. The invention can be used for applications other than a vehicle and for example for any industrial or personal equipment requiring braking.Although here the crown of the stator is formed of a single ring of electromagnets (the electromagnets extending successively in the circumferential direction in the following order: north electromagnet, east electromagnet, south electromagnet, west electromagnet), the crown of the stator may be formed of at least two rings of electromagnets extending successively along the X axis (knowing that for each ring the electromagnets then extend successively in the circumferential direction in the following order: north electromagnet, east electromagnet, south electromagnet, west electromagnet).

Claims

CLAIMS 1. Vehicle wheel (1), rotatably mounted on an axle (E), comprising: − an annular rim (2) connected by a disc (3) to a hub (4) pivotally received on the axle, the rim delimiting with the hub an annular space closed by the disc; − a radial flux electric motor (10) comprising a first stator (11) and a first rotor (12) arranged coaxially with the wheel to produce between them a first magnetic flux capable of generating a torque for driving the wheel in rotation; − a magnetic brake (20); characterized in that the electric motor and the magnetic brake extend into each other inside the annular space, the first rotor (12) also serving as a rotor for the magnetic brake so as to produce with a stator of the magnetic brake a second magnetic flux capable of generating eddy currents generating a braking torque of the wheel, the stator of the magnetic brake being thus arranged coaxially with the wheel (1),or the first stator (11) also serving as a stator for the magnetic brake so as to produce with a rotor of the magnetic brake a second magnetic flux capable of generating eddy currents generating a braking torque of the wheel, the rotor of the magnetic brake being thus arranged coaxially with the wheel (1), in which the first stator (11) or the first rotor (12) comprises a Halbach network formed at least in part by electromagnets, that of the first stator (11) or the first rotor (12) comprising the Halbach network being that also serving as stator, respectively rotor, for the magnetic brake.

2. Wheel according to claim 1, in which one of the, first or second rotor is adjacent to the rim (2) and the other of the first rotor and the second rotor is adjacent to the hub (4), the first stator (11) and the second stator extending between the first rotor (12) and the second rotor.

3. Wheel (1) according to claim 1 or claim 2, wherein the first stator (11) and the second stator are radially opposite each other.

4. Wheel (1) according to claim 3, wherein the first stator (11) extends inside the second stator.

5. Wheel (1) according to one of the preceding claims, wherein the first rotor (12) comprises permanent magnets and / or electromagnets capable of interacting with the electromagnets equipping the first stator (11).

6. Wheel (1) according to claim 5, in which the Halbach network is formed by a succession of electromagnets extending circumferentially around the hub (4) and / or extending axially along the hub (4). 7.Wheel (1) according to one of the preceding claims, in which the second rotor is formed by the rim (2) made of electrically conductive material or is formed by a local coating arranged on an internal periphery of said rim (2), the coating being made of electrically conductive material.

8. Aircraft (A) landing gear (P) comprising at least one wheel (1) according to any one of the preceding claims.

9. Aircraft (A) comprising at least one landing gear (P) according to claim 8.

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