Wheel with combined magnetic / friction braking for a vehicle, and aircraft landing gear and aircraft which are equipped with such a wheel

Abstract

The invention relates to a vehicle braked wheel (1) mounted on an axle (E) so as to be rotatable about an axis (X), and comprising: − a first, magnetic, braking device (10) comprising a stator (11) and a rotor (12) which are capable of producing a first braking torque, one of either the stator or the rotor being arranged to move along the axis (X) between a position of free rotation and a braking position; − a second, friction, braking device (20) comprising a stack of discs (21.1, 21.2, 21.3, 22.1, 22.2) capable of producing a second braking torque, the stack of discs axially facing a rear face (11AR) of whichever of the stator or of the rotor is arranged to move along the axis; and − at least one actuator (51) designed to exert a pressing force on a front face (11AV) of whichever of the stator or of the rotor is arranged to move along the axis.

Description

[0001]MIXED MAGNETIC / FRICTION BRAKING WHEEL FOR VEHICLE; AIRCRAFT LANDING GEAR AND AIRCRAFT EQUIPPED WITH SUCH A WHEEL The present invention relates to the field of braking vehicle wheels such as aircraft wheels. The invention applies more particularly to mixed magnetic / friction braking devices, i.e. devices in which a magnetic field and mechanical friction are used simultaneously or selectively to produce a braking force. BACKGROUND OF THE INVENTION An aircraft wheel generally comprises a rim connected by a web to a hub which is mounted to rotate on an axle carried by a lower end of a landing gear. The aircraft wheel is traditionally provided with a braking device for slowing and immobilizing the aircraft when it is on the ground. Friction braking devices are known comprising a stack of braking discs which is housed in a space extending between the rimand the hub and which comprises an alternation of rotor discs linked in rotation to the wheel and stator discs fixed in rotation relative to the axle. The braking device also comprises hydraulic or electromechanical actuators mounted on an actuator-carrying ring and arranged to selectively apply a pressing force on the stack of discs so as to brake the rotation of the wheel. Eddy current magnetic braking devices are also known, used for braking vehicle wheels and more particularly aircraft wheels. The magnetic braking device generally comprises a rotor which is attached to the wheel opposite a stator mounted fixed in rotation and sliding relative to the axle. One of the rotor and the stator is provided with magnets while the other of said rotor and said stator is made of an electrically conductive material. The sliding of the stator isgenerally subject to hydraulic or electromechanical actuators arranged to selectively bring said stator closer to the rotor so as to generate a braking torque on said rotor and thus brake the rotation of the wheel. Document FR-A-3122405 describes such a magnetic braking device. Unlike friction braking devices, eddy current braking devices are not subject to wear, which limits their maintenance and the emission of fine particles. However, eddy current braking devices can only be used when the rotor has a certain speed relative to the stator. It therefore seemed sensible to associate the magnetic braking device with a friction braking device to ensure braking at low speed or when parking. However, this association tends to require the integration of a first control system to actuate the friction braking device, andof a second control system, independent of the first control system, to operate the eddy current braking device, which tends to complicate the control of the brake, but also to increase its weight and complicate its integration into the wheel. However, climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft but also to those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Aviation manufacturers have been mobilizing for several years now to make a contribution to the fight against climate change. Technological research efforts have already led to significant improvementsvery significant the environmental performance of aircraft. 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 aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft. This sustained research and development work relates in particular to the lightening of aircraft, in particular through the materials used, the simplification and lightening of on-board equipment. OBJECT OF THE INVENTION The invention results from this work and aims to propose a vehicle wheel with mixed braking that at least partially overcomes the aforementioned drawbacks. SUMMARY OF THE INVENTION To this end, the invention proposes a braked vehicle wheel mounted for rotation on an axle around an axis, comprising: − afirst magnetic braking device, comprising a stator and a rotor arranged to produce between them a magnetic flux capable of generating eddy currents producing a first braking torque of the wheel, one of the stator and the rotor being arranged to move along the axis of rotation of the wheel between a position of free rotation of the wheel and a braking position of the wheel; − a second braking device, by friction, comprising a stack of discs comprising at least one stator disc and one rotor disc arranged to rub against each other while producing a second braking torque of the wheel, the stack of discs being axially opposite a rear face of the stator or the rotor arranged to move along the axis of rotation of the wheel; and − at least one actuator arranged to cause the stator or the rotor to move from the position of free rotation to the braking position and to exert on a front face of said stator orof said rotor a sufficient pressing force to force all of the discs to rub against each other. The pressing force exerted by the actuator is thus capable of simultaneously producing the first braking torque and the second braking torque, so that a single control system can control both the first braking device and the second braking device. The integration, operation and implementation of the wheel braking system are therefore facilitated and simplified, and the overall volume of said braking system is limited. According to a particular characteristic, the first braking device is radial flux. In particular, the stator and the rotor respectively comprise at least a first main surface and a second main surface arranged to fully engage with each other throughout the use and wear of the stator disc and the rotor disc. According to aanother particular characteristic, the braked wheel comprises at least one connecting element connecting the other of the stator and the rotor to the stator disc or to the rotor disc to ensure its translational coupling with said stator disc or said rotor disc along the axis of rotation of the wheel. According to another particular characteristic, the wheel comprises an annular rim connected by a web to a hub pivotally received on the axle, the rim delimiting with the web and the hub an annular space in which the first braking device and the second braking device extend. According to another particular characteristic, the elastic return means comprise at least one spring. According to another particular characteristic, the stator disc is slidably mounted along the axis of rotation of the wheel on a torsion tube fixed to the axle. In particular, the stator is slidably mounted along the axis of rotation of the wheel on the torsion tube.According to another particular characteristic, the actuator is a hydraulic actuator. The invention also relates to an aircraft landing gear comprising at least one such wheel. The invention also relates to an aircraft comprising at least one such landing gear. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood in the 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 braked wheels according to a particular embodiment of the invention; [Fig. 2] Figure 2 is an axial sectional view of one of the braked wheels of the aircraft illustrated in Figure 1; [Fig. 3] Figure 3 is an exploded view of the braked wheel illustrated in Figure 2; [Fig. 4] Figure 4 is a perspective view of the first and second braking devices of the braked wheel illustrated in Figure 2; [Fig. 5] Figure 5is a simplified representation, in axial section, of the first and second braking devices of the braked wheel illustrated in Figure 2, illustrating the wear of the first braking device. DETAILED DESCRIPTION OF THE INVENTION With reference to Figure 1, the invention is described in application to an aircraft A comprising two main landing gears P which each comprise a leg J ​​having a first end articulated on a structure S of the aircraft A and, opposite, a second end carrying wheels 1 rotating around an axis X on a tubular axle E. The main landing gears P are here of the retractable type but the invention is applicable to fixed landing gears, or even to another type of vehicle such as a land vehicle. The wheels 1 are said to be “braked”, that is to say equipped with a brake intended to selectively slow down and stop the aircraft A when it is on the ground. The following description relates to one of the wheels 1 of the aircraft, the wheels 1being identical here but may also be different. The wheel 1 comprises, as illustrated in Figure 2, an annular rim 2 connected by a disc 3 to a hub 4 pivotally received on the axle E by means of bearings (not shown). The rim 2 extends opposite the hub 4 and delimits with said hub 4 an annular space having one end at least partially closed by the disc 3 and, opposite, an open end. The brake of the wheel 1 comprises a first radial flux magnetic braking device 10 and a second friction braking device 20. The second braking device 20 is arranged between the first braking device 10 and the disc 3 of the wheel 1. The second braking device 20 comprises, in a manner known per se, brake discs, including stator discs 21.1, 21.2, 21.3 and rotor discs 22.1, 22.2 which are stacked alternately with each other on a torsion tube 30 fixed to a collar E1 ofthe axle E. The stator discs 21.1, 21.2, 21.3 and the rotor discs 22.1, 22.2 extend inside the annular space delimited by the wheel 1 and are here made of carbon or steel. The stator discs 21.1, 21.2, 21.3 comprise in particular a first stator disc 21.1 and a last stator disc 21.3 between which the rotor discs 22.1, 22.2 and the other stator disc 21.2 extend. With reference to Figure 3, the stator discs 21.1, 21.2, 21.3 have an internal periphery comprising axial peripheral notches 21a each receiving a section of a tenon (not shown) which is integral with the outer surface of the torque tube 30 to ensure rotational coupling of the stator discs 21.1, 21.2, 21.3 with the torque tube 30 around the axis X. The rotor discs 22.1, 22.2 have an external periphery comprising axial peripheral notches 22a each receiving a section of a bar 5 fixed on the surfaceinner surface of the rim 2 to ensure rotational coupling of the rotor discs 22.1, 22.2 with the rim 2 around the axis X. The first braking device 10 comprises a fixed rotating element, or stator 11, and a mobile rotating element, or rotor 12. The stator 11 and the rotor 12 here have respectively the shape of an annular disc and a crown having central axes coincident with the axis X of rotation of the wheel 1. With reference to FIG. 3, the rotor 12 has an external periphery which comprises axial peripheral grooves 12a each receiving an end section of the bars 5 fixed on the inner surface of the rim 2 to ensure rotational coupling of the rotor 12 with the rim 2 around the axis X. Connecting elements 40 connect the rotor 12 to the rotor disc 22.1 to ensure translational coupling of said rotor 12 with said rotor disc 22.1 along the X axis. As illustrated in Figure 4, the connecting elements 40 extend in theaxial peripheral grooves 12a, 22a of the rotor 12 and of the rotor disc 22.1, and are distributed equally around the axis X of rotation of the wheel 1. The crown forming the rotor 12 comprises an internal periphery provided with a first ring 12.1 and a second ring 12.2 made of an electrically conductive material and respectively defining a first main surface 12.11 and a second main surface 12.22 of the rotor 12. This first main surface 12.11 and this second main surface 12.22 are cylindrical in shape and extend coaxially with the wheel 1. The first ring 12.1 and the second ring 12.2 are here substantially identical. The stator 11 has an internal periphery which comprises axial peripheral notches 11a each receiving a section of the tenons secured to the external surface of the torsion tube 30 to ensure rotational coupling of the stator 11 with the torsion tube 30 around the axis X and translational guidance of saidstator 11 on the torque tube 30 along said axis X. The disc forming the stator 11 comprises an external periphery provided with a first series of permanent magnets 11.1 and a second series of permanent magnets 11.2 respectively defining a first main surface 11.11 and a second main surface 11.22 of the stator 11. This first main surface 11.11 and this second main surface 11.22 are cylindrical in shape and extend coaxially with the wheel 1 so as to be able to be respectively engaged in the first main surface 12.11 and the second main surface 12.22 of the rotor 12. The magnets 11.1, 11.2 are arranged so as to generate eddy currents in the rotor 12 when the first and second main surfaces 11.11, 11.22 of the stator 11 and the first and second main surfaces 12.11, 12.22 of the rotor 12 are separated by a small air gap and that said rotor 12 pivots relative to said stator 11. The tenons formslides allowing the stator 11 to slide along the X axis on the torque tube 30 between a first position called braking (not shown) and a second position called free rotation of the wheel 1 (shown in Figure 2). In the braking position, the stator 11 is brought closer to the rotor 12 to the point that the first and second main surfaces 11.11, 11.22 of the stator 11 are engaged in the first and second main surfaces 12.11, 12.22 of the rotor 12: the first main surfaces 11.11, 12.11 and the second main surfaces 11.22, 12.22 are separated from each other by a first predetermined air gap. In the free-rotating position, the stator 11 is spaced from the rotor 12 to the point that the first and second main surfaces 11.11, 11.22 of the stator 11 are clear of the first and second main surfaces 12.11, 12.22 of the rotor 12: the first main surfaces 11.11, 12.11 and the second main surfaces 11.22, 12.22 areseparated from each other by a second predetermined air gap which is greater than the first air gap. It is understood that in the braking position, the magnets 11.1, 11.2 of the stator 11 generate in the rotor 12 eddy currents sufficient to generate a braking torque on said rotor 12, and that in the free rotation position, this braking torque is negligible, or even non-existent. It will be noted that the stator 11 is axially opposite the first stator disc 21.1 and that it comprises a rear face 11ar which is in contact with said first stator disc 21.1 when said stator 11 is in the braking position. The brake further comprises hydraulic actuators 51 (here four in number) which are carried by an actuator-carrying ring 50 fixed to one end of the torque tube 30. The actuators 51 are identical to each other and have centers inscribed on the same circle, the center of which is located on the axis X of rotation of the wheel 1. Each of theactuators 51 comprises a piston 51.1 received in a cylindrical cavity 50.1 of the actuator-carrying ring 50. The cavities 50.1 are distributed equally around the axis X of rotation of the wheel 1 and the pistons 51.1 comprise a free end fixed by screwing to a front face 11AV of the stator 11, opposite the rear face 11AR. The pistons 51.1 are movable in translation along an axis parallel to the axis X of rotation of the wheel 1 to: − cause the stator 11 to move from the free rotation position to the braking position so as to generate a first braking torque on the wheel 1 via the rotor 12; and − exert on the front face 11AV of the stator 11 a sufficient pressing force to force all of the discs 21.1, 21.2, 21.3, 22.1, 22.2 to rub against each other (when the stator 11 is in the braking position) so as to generate a second braking torque on the wheel 1 via the rotor discs 22.1, 22.2. The equitable distributionactuators 51 around the X axis makes it possible to distribute the pressing forces exerted by the pistons 51.1 fairly on the stack of discs 21.1, 21.2, 21.3, 22.1, 22.2 via the stator 11. It is understood that: − the sliding of the stator 11 between the free rotation position and the braking position is subject to the actuators 51; − the friction of the discs 21.1, 21.2, 21.3, 22.1, 22.2 against each other is subject to the actuators 51 via the stator 11; − when the stator 11 is between the free rotation position and the braking position, the second braking torque generated by friction is substantially zero; − as soon as the stator 11 is in the braking position, the first braking torque generated by the eddy currents is maximum and the second braking torque generated by friction is a function of the pressing forces exerted by the actuators 51 on the stator 11; and − the first braking torque and the second braking torque arecumulative. It is thus possible to have more or less friction braking (the second braking device 20 is not necessarily fully engaged) while the magnetic braking is maximum (the first braking device 10 is fully engaged), which makes it possible to use the second braking device 20 more or less and therefore to limit the wear of the discs 21.1, 21.2, 21.3, 22.1, 22.2 in situations where the first braking device 10 is sufficient to slow the wheel 1. In other words, the second braking device 20 can be used substantially only when necessary, in particular in speed ranges of the wheel 1 where the first braking device 10 is the least effective, or even at energy levels which require the use of both the first braking device 10 and the second braking device 20, for example during a takeoff interruption also called RTOfor “Rejected Take Off”. The friction of the discs 21.1, 21.2, 21.3, 22.1, 22.2 causes, in a manner known per se, wear of the various friction faces of the stator discs 21.1, 21.2, 21.3 and the rotor discs 22.1, 22.2, and therefore a reduction in their thickness. This wear is compensated by: − a take-up device (not shown) commonly used so that the actuation stroke, and therefore the actuation time, of the pistons 51.1 is identical at each new braking, throughout the use and wear of the discs 21.1, 21.2, 21.3, 22.1, 22.2; and − the connecting elements 40 which guarantee the release and complete engagement of the magnets 11.1, 11.2 of the stator 11 in the electrically conductive rings 12.1, 12.2 of the rotor 12 so that the first braking torque generated by the eddy currents is respectively negligible and maximum, throughout the use and wear of the discs 21.1, 21.2, 21.3, 22.1, 22.2. It will be notedthat the dimensioning of the magnets 11.1, 11.2 and the electrically conductive rings 12.1, 12.2 must take into account the maximum wear of the discs 21.1, 21.2, 21.3, 22.1, 22.2 so that the engagement of said magnets 11.1, 11.2 in said rings 12.1, 12.2 is complete throughout the use and wear of the discs 21.1, 21.2, 21.3, 22.1, 22.2. In particular, the thicknesses e12.11, e12.22, along the X axis, of the main surfaces 12.11, 12.22 of the rings 12.1, 12.2 must be, as illustrated in Figure 5 (where only one of the series of magnets and the corresponding ring are shown), greater than those e11.11, e11.22 of the main surfaces 11.11, 11.22 of the magnets 11.1, 11.2 so that: − when the discs 21.1, 21.2, 21.3, 22.1, 22.2 are new (Figure 5, left side), the magnets 11.1, 11.2 are fully engaged in the rings 12.1, 12.2 at a distance from the first stator disc 21.1; and − when discs 21.1, 21.2, 21.3, 22.1, 22.2 areworn (figure 5, right side), the magnets 11.1, 11.2 are fully engaged in the rings 12.1, 12.2 near the first stator disc 21.1. 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 rotor 12 can be integrated into the wheel 1, and therefore not linked in translation to the rotor disc 22.1 via the connecting elements 40. Although the stator 11 is here linked in translation to the first rotor disc 22.1, it can be linked in translation to the second rotor disc 22.2, or more generally to any disc in the stack of discs. Although the first magnetic braking device 10 is here radial flux (the stator 11 and the rotor 12 have only axial surfaces as main surfaces 11.11, 11.22, 12.11, 12.22), it can also be axial flux (the stator 11 and the rotor 12 have only axial surfaces as main surfacesradial) or combine radial and axial fluxes. The magnets 11.1, 11.2 may be carried by the rotor 12 instead of the stator 11. The stator 11 then carries the rings 12.1, 12.2 made of or covered with an electrically conductive material. The magnets 11.1, 11.2 may be permanent magnets, electromagnets or a combination of both. Although the stator 11 is here provided with two series of magnets 11.1, 11.2, it may comprise only one series of magnets or more than two series of magnets. The rotor 12 will then comprise one or more than two rings 12.1, 12.2 made of a conductive material. Although the relative approach of the stator 11 and the rotor 12 along the axis X is here achieved by sliding said stator 11 on the torque tube 30, it can also be achieved by sliding said rotor 12 on the rim 2. The stator 11 is then connected to one of the stator discs 21.1, 21.2, 21.3 so as to ensure translational coupling of said stator 11 with the discstator 21.1, 21.2, 21.3 chosen. The number of stator discs 21.1, 21.2, 21.3 and the number of rotor discs 22.1, 22.2 may be different from those described and illustrated. Although the stator discs 21.1, 21.2, 21.3 and the rotor discs 22.1, 22.2 are here made of carbon or steel, they may be made of any other material suitable for the intended application. The actuator ring 50 may be fixed directly to the axle E. The torque tube 30 may be fixed to the actuator ring 50 or to the leg J. The number of actuators 51 may be different from that described and illustrated. Although the actuators 51 are here carried by the same actuator-carrying ring 50, they can also be carried directly by the torque tube 30. Although the actuators 51 are here hydraulic, they can also be electric, pneumatic, etc. The pistons 51.1 of the actuators 51 can be replaced by any other equivalent means capable of ensuringthis function. The invention can be used on any type of vehicle, whether air, land or amphibious. The invention can be used for applications other than a vehicle and for example for any equipment, industrial or personal, requiring braking.

Claims

CLAIMS 1. Braked vehicle wheel (1) mounted for rotation on an axle (E) about an axis (X), comprising: − a first magnetic braking device (10), comprising a stator (11) and a rotor (12) arranged to produce between them a magnetic flux capable of generating eddy currents producing a first braking torque of the wheel, one of the stator and the rotor being arranged to move along the axis (X) of rotation of the wheel between a position of free rotation of the wheel and a braking position of the wheel; − a second braking device (20), by friction, comprising a stack of discs comprising at least one stator disc (21.1, 21.2, 21.3) and one rotor disc (22.1, 22.2) arranged to rub against each other while producing a second braking torque of the wheel, the stack of discs being axially opposite a rear face (11 AR) of the stator or rotor arranged to move along the axis of rotation of the wheel; and − at least one actuator (51) arranged to cause the stator or rotor to move from the free rotation position to the braking position and exert on a front face (11 AV ) of said stator or said rotor a pressing force sufficient to force all of the discs to rub against each other.

2. Wheel (1) according to claim 1, wherein the first braking device (10) is radial flux.

3. Wheel (1) according to claim 2, wherein the stator (11) and the rotor (12) respectively comprise at least a first main surface (11.11, 11.22) and a second main surface (12.11, 12.22) arranged to fully engage with each other throughout use and wear of the stator disc (21.1, 21.2, 21.3) and the rotor disc (22.1, 22.2).

4. Wheel (1) according to any one of the preceding claims, comprising at least one connecting element (40) connecting the other of the stator (11) and the rotor (12) to the stator disc (21.1, 21.2, 21.3) or to the rotor disc (22.1, 22.2) to ensure its translational coupling with said stator disc or said rotor disc along the axis (X) of rotation of the wheel.

5. Wheel (1) according to any one of the preceding claims, comprising an annular rim (2) connected by a web (3) to a hub (4) pivotally received on the axle (E), the rim delimiting with the web and the hub an annular space in which the first braking device (10) and the second braking device (20) extend.

6. Wheel (1) according to any one of the preceding claims, in which the stator disc (21.1, 21.2, 21.3) is slidably mounted along the axis (X) of rotation of the wheel on a torsion tube (30) fixed to the axle (E).

7. Wheel (1) according to claim 6, wherein the stator (11) is slidably mounted along the axis (X) of rotation of the wheel on the torque tube (30).

8. Wheel (1) according to any one of the preceding claims, wherein the actuator (51) is a hydraulic actuator.

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

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

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