MAGNETIC BRAKE DEVICE USING EDDY CURRENT, BRAKE WHEEL OF A VEHICLE AND LANDING GEAR OF AN AIRCRAFT WITH SUCH A WHEEL

Description

[0001] The present invention relates to the field of braking vehicle wheels such as aircraft wheels. BACKGROUND OF THE INVENTION

[0002] An aircraft wheel typically comprises a rim connected by a web to a hub mounted for rotation on a wheel support shaft (axle or spindle).

[0003] Friction braking devices are known comprising a stack of braking discs which is housed in a space extending between the rim and the hub and which comprises an alternation of rotor discs linked in rotation with the wheel and stator discs fixed relative to the wheel support. The braking device also comprises hydraulic or electromechanical actuators mounted on an actuator holder and arranged to apply a controlled braking force to the stack of discs so as to brake the rotation of the wheel.

[0004] It has been proposed, in particular in document FR-A-2953196, to equip such braked wheels with an electromagnetic auxiliary brake ensuring energy dissipation by means other than mechanical friction.

[0005] Eddy current magnetic braking devices are also known, used for braking vehicle wheels and more particularly aircraft wheels. Document WO-A-2014 / 029962 describes such a device comprising a rotor which is provided with one or more magnets and which is mounted opposite an electromagnetic stator.

[0006] Document US-A-20200300310 also describes an eddy current magnetic braking device.

[0007] Furthermore, document EP-A-3309944 discloses an eddy current brake comprising magnets having different widths.

[0008] Generally speaking, the performance of an eddy current magnetic braking device depends on the power of the magnets used and their dimensions. The braking device is therefore relatively heavy and bulky when the maximum braking power required is high. This is the case, for example, for use on aircraft, even though mass and size are severe constraints for this use. SUBJECT OF THE INVENTION

[0009] The invention aims in particular to propose an eddy current magnetic braking device which at least partially overcomes the aforementioned drawbacks. SUMMARY OF THE INVENTION

[0010] To this end, the invention provides an eddy current magnetic braking device, comprising at least one fixed element and one element movable relative to the fixed element in a direction of movement, having a surface facing a surface of the fixed element, one of the elements comprising a plurality of magnets capable of generating eddy currents in the other of the elements, made of electrically conductive material, when the two elements are in relative movement. The plurality of magnets comprises first magnets having a first magnetization vector substantially perpendicular to the facing surfaces and being separated two by two by a second magnet having a second magnetization vector substantially perpendicular to the first magnetization vectors of the first two magnets between which the second magnet is located.The magnets have widths such that the first magnets are spaced two by two by a first distance less than a second distance separating the second magnets two by two and the first magnets have a length measured in a direction perpendicular to their width and locally parallel to the facing surfaces which is greater than a length of the second magnets measured in a direction perpendicular to their width and locally parallel to the facing surfaces, the length of the second magnets being approximately 70% that of the first magnets.

[0011] This arrangement of magnets optimizes and concentrates the magnetic flux produced by the first magnets by reducing the return path of the magnetic flux that passes through the second magnets. The smaller width of the second magnets surprisingly allows for an increase in the eddy currents generated and therefore an increase in the braking torque provided. This also has the advantage of limiting the mass and size of the device.

[0012] The invention also relates to a braked wheel equipped with such a device and a landing gear equipped with such a wheel.

[0013] Other characteristics and advantages of the invention will emerge from reading the following description of particular and non-limiting embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Reference will be made to the attached drawings, including: [ Fig. 1 ] there figure 1 is a partial schematic view of an aircraft equipped with a landing gear according to the invention; [ Fig. 2 ] there figure 2 is a partial schematic view, in axial section, of a wheel equipped with a braking device according to a first embodiment of the invention; [ Fig. 3 ] there figure 3 is a partial schematic view, in axial section, of a wheel equipped with a braking device according to a second embodiment of the invention; [ Fig. 4 ] there figure 4 is a partial schematic view of an arrangement of magnets according to a particular embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] In reference to the figures 1 à 3 , the braking system according to the invention is carried by an aircraft 100 comprising landing gears 101. Each landing gear 101 comprises a leg having one end provided with two coaxial shafts 102 on each of which a wheel 103 is mounted to pivot. Each wheel 103 comprises, in a manner known per se, a hub 104 mounted to pivot on the shaft 102 and a rim 105 connected to the hub 104 by a web 106.

[0016] According to the invention, the wheels 103 are equipped with a magnetic braking device generally designated 1. The magnetic braking device 1 comprises fixed elements, or stators 2, and mobile elements, or rotors 3.

[0017] More precisely here, the stators 2 and the rotors 3 are in the form of discs, coaxial with the wheel 103, therefore having collinear central axes. The stators 2 are linked in rotation to the shaft 103 or to the leg 102, here by means of a torque tube 4, while the rotors 3 are linked in rotation to the wheel 104, for example to the rim of the wheel 104. Thus, in each pair, each rotor 3 rotates on itself around its central axis relative to the stator 2: during this movement of the rotor 3 in a circumferential direction, the main face 3.1 remains opposite the main face 2.1 and parallel to it.

[0018] According to the first embodiment of the braking device shown in the figure 2 , the stators 2 and the rotors 3 are arranged in pairs: each stator 2 has a main face 2.1 extending opposite a main face 3.1 of one of the rotors 3. The faces 2.1, 3.1 are parallel to each other.

[0019] The stators 2 are mounted on a slide 5 sliding on the torsion tube 4 to be movable in an axial direction of the torsion tube 4 between a first position in which the rotor 3 and the stator 2 of each pair are close to each other and have their main faces 3.1, 2.1 separated by a first predetermined air gap and a second position in which the rotor 3 and the stator 2 of each pair are spaced apart from each other and have their main faces 3.1, 2.1 separated by a second predetermined air gap greater than the first predetermined air gap. At least one electromechanical actuator 6 controllable by the pilot of the aircraft in a manner known per se moves the slide 6 between the two aforementioned positions. An axial stop, of the rolling bearing or needle roller type, is provided between the rotors 3 and the stators 2 to ensure that the stators 2 cannot be brought closer to the rotors 3 beyond the first air gap.

[0020] According to the second embodiment of the braking device shown in the figure 3 , the stators 2 and the rotors 3 are arranged in triplets, only one of which is shown here: each rotor 3 is arranged between two stators 2 each having a main face 2.1 extending opposite a main face 3.1 of the rotor 3. The faces 2.1, 3.1 are parallel to each other.

[0021] The stators 2 are rotationally connected to the shaft 102 or to the leg of the landing gear 101, here by means of a torque tube 4, while the rotors 3 are rotationally connected to the wheel 103, here to the rim 105 of the wheel 103. Thus, in each triplet, each rotor 3 rotates on itself around its central axis relative to the stators 2 which frame it: during this movement of the rotor 3 in a circumferential direction, the main faces 3.1 remain opposite the main faces 2.1 and parallel to them.

[0022] Each of the stators 2 is mounted on a slide 5 sliding (without rotation) on the torque tube 4 to be movable in an axial direction of the torque tube 4 between a first position in which the rotor 3 and the stator 2 are close to each other and have their main faces 3.1, 2.1 separated by a first predetermined air gap and a second position in which the rotor 3 and the stator 2 are spaced apart from each other and have their main faces 3.1, 2.1 separated by a second predetermined air gap greater than the first predetermined air gap. At least one electromechanical actuator 6, controllable by the pilot of the aircraft in a manner known per se, moves the slide 5 between the two aforementioned positions.An axial stop, of the rolling bearing or needle roller type, is provided, interposed between the rotors 3 and the stators 2 (or between parts linked to them) to ensure that the stators 2 cannot be brought closer to the rotors 3 beyond the first air gap.

[0023] In these two embodiments, the rotors 3 and stators 2 are constituted in the same way.

[0024] The rotors 3 are made of copper or any other electrically conductive material.

[0025] In reference to the figures 4 and 5 also, each stator 2 comprises a plurality of magnets capable of generating eddy currents in the rotor 3 when the stator 2 is in the first position and the rotor 3 pivots opposite the stator 2. The magnets, here based on rare earths, are for example 16 in number and are preferably fixed on a magnetic steel support, or even on a non-magnetic support. The thickness of the support is preferably relatively small while satisfying the thermal and mechanical constraints.

[0026] The plurality of magnets comprises first magnets 11, 13 having a first magnetization vector substantially perpendicular to the main face 2.1 and being separated two by two by a second magnet 12, 14 having a second magnetization vector substantially perpendicular to the first magnetization vectors of the two first magnets 11, 13 between which the second magnet 12, 14 is located. More precisely, the magnets 11, 12, 13, 14 have angular sector shapes and have a length L measured in a radial direction of the stator 2 and an average width l measured in a locally tangential direction of the discs (i.e. perpendicular to the direction of the length L) at half of said length L. The lengths L and widths l are measured in directions locally parallel to the facing surfaces (the main faces 2.1, 3.1).

[0027] The magnets 11, 12, 13, 14 are arranged in a Halbach pattern, alternating along the circumferential direction of the stator 2 as follows: a magnet 11, a magnet 12, a magnet 13, a magnet 14, a magnet 11, a magnet 12, a magnet 13, a magnet 14, a magnet 11 and so on... It is recalled that the magnetization vector indicates the direction of the magnetic field generated by a magnet and extends in the magnet from the South pole to the North pole. In this case: each magnet 11 has its magnetization vector which leaves the main face 2.1 (its North pole opens onto the main face 2.1), each magnet 12 has its magnetization vector which extends from the neighboring magnet 11 towards the neighboring magnet 13, each magnet 13 has its magnetization vector which enters the main face 2.1 (its South pole opens onto the main face 2.1), each magnet 14 has its magnetization vector which extends from the neighboring magnet 11 towards the neighboring magnet 13.

[0028] It is understood that the magnets 12, 14 arranged on each side of the same magnet 11 have their magnetization vector in opposite directions.

[0029] The magnets 11, 12, 13, 14 have widths l 11 , l 12 , l 13 , l 14 such that the first magnets 11, 13 are spaced two by two by a first distance less than a second distance separating the second magnets 12, 14 two by two. The best results are obtained when the width l 12 , l 14 of the second magnets 12, 14 is approximately 70% of those l 11 , l 13 of the first magnets 11, 13.

[0030] In reference to the figure 4 , the lengths L 11 , L 13 of the magnets 11, 13 are identical to each other and the lengths L 12 , L 14 of the magnets 12, 14 are identical to each other. The lengths L 11 , L 13 of the magnets 11, 13 are greater than the lengths L 12 , L 14 of the magnets 12, 14. Preferably, the length L 12 , L 14 of the second magnets 12, 14 is 70% that of the first magnets 11, 13.

[0031] In the arrangement shown in the figure 4 , the magnets 12, 14 are positioned symmetrically on a circle passing through the geometric center of the North poles of the magnets 11 and the South poles of the magnets 13.

[0032] It is understood that the magnets 12, 14 occupy a smaller surface area on the main face 3.1 than that of the magnets 11, 13.

[0033] The arrangement of the magnets 11, 12, 13, 14 makes it possible to optimize and concentrate the magnetic flux produced by the magnets 11, 13 by reducing the return path of the magnetic flux which passes through the magnets 12, 14 and not through the support whose mass can be reduced since it does not need to provide a magnetic flux conduction function.

[0034] Compared to the prior art, the invention allows an increase in the braking torque provided while limiting the mass and size of the device.

[0035] In addition, the manufacturing of second magnets is made easier.

[0036] It is understood that to cause braking, the electromechanical control actuators are driven to bring the stators 2 into the first position and that, to interrupt braking, the electromechanical control actuators are driven to bring the stators 2 into the second position, a position in which the magnets do not allow sufficient eddy currents to be generated in the rotors to cause braking of the rotors. It will be noted that below a certain rotational speed of the rotors 3, the braking torque is negligible regardless of the position of the stators. It may then be necessary to consider an additional brake.

[0037] 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.

[0038] In particular, the device may have a structure different from that described.

[0039] Magnets can be carried by the rotor instead of the stator.

[0040] The shape and dimensions of the magnets may be different from those described. Preferably, the first magnets 11, 13 will represent approximately 70% of the surface area of ​​the element that carries them, but this is not mandatory.

[0041] The number of rotors and / or the number of stators may be different from those mentioned.

[0042] The device described is axial flux but the invention is applicable to radial flux operation. Thus, although the rotor and stator have been described in the form of parallel discs facing each other, the stator and rotor may have other shapes. They may, for example, be arranged in the form of an outer drum and an inner drum engaged in the outer drum in such a way that the inner drum has an outer surface facing an inner surface of the outer drum. The magnets are carried by the outer surface of the inner drum or by the inner surface of the outer drum.

[0043] The magnetic braking device according to the invention can be associated with a conventional friction braking device which comprises friction members, for example a stack of carbon discs, and a plurality of electromechanical actuators carried by an actuator holder. Each electromechanical actuator comprises an electric motor and a pusher capable of being moved by the electric motor to press the stack of discs. The electromechanical actuator is thus intended to produce a controlled braking force on the stack of discs. A method of controlling the braking devices is for example known from document FR-A-2953196.

[0044] Alternatively, the magnets can be directly attached to the rotor discs or stator discs of the friction brake to slow the wheel by magnetic braking when the discs are spaced apart by a suitable air gap.

[0045] It is possible to use for the mechanical actuation of the magnetic braking device a separate actuator for each stator rather than an actuator acting on a slide carrying several stators.

[0046] Other methods of actuation of the magnetic brake are possible: mechanical, for example, by axially moving the rotors and no longer the stators, or electromagnetic by means of coils generating a magnetic field cancelling that of the permanent magnets.

[0047] The invention can be used on any type of vehicle.

[0048] The length of the second magnets (12, 14) is approximately 70% that of the first magnets (11, 13), i.e. 70% to within a few tenths of a percent or within a few percent.

Claims

1. Eddy current magnetic braking device, comprising at least one stationary element (2) and one movable element (3) with respect to the stationary element (2) in a movement direction, by having a surface (3.1) opposite a surface of the stationary element (2), one (2) of the elements comprising a plurality of magnets (11, 12, 13, 14) capable of generating eddy currents in the other (3) of the elements, made of electrically conductive material, when the two elements (2, 3) are in relative movement, wherein the plurality of magnets comprises first magnets (11, 13) and second magnets (12, 14) disposed alternating, the first magnets (11, 13) having a first magnetisation vector substantially perpendicular to the opposite surfaces (2.1, 3.1) and each of the second magnets (12, 14) having a second magnetisation vector substantially perpendicular to the first magnetisation vectors of two first magnets (11, 13), between which it is located, and the magnets (11, 12, 13, 14) have widths such that the first magnets (11, 13) are spaced apart in pairs by a first distance less than a second distance separating the second magnets (12, 14) in pairs, characterized in that the first magnets (11, 13) have a length measured in a direction perpendicular to their width and locally parallel to the opposite surfaces (2.1, 3.1) which is greater than a length of the second magnets (12, 14) measured in a direction perpendicular to their width and locally parallel to the opposite surfaces (2.1, 3.1), the length of the second magnets (12, 14) being around 70% that of the first magnets (11, 13).

2. Device according to claim 1, wherein the width of the second magnets (12, 14) is around 70% that of the first magnets (11, 13).

3. Device according to claim 1, wherein the first magnets (11, 13) represent around 70% of the surface (2.1) of the element (2) which carries them.

4. Device according to claim 1, wherein the elements (2, 3) have a disc shape and have colinear central axes, the movable element (3) having a main face (3.1) opposite a main face (2.1) of the stationary element (2), thus forming the opposite surfaces and the movable element (3) pivoting on its central axis, each first vector extending perpendicularly to the main faces (2.1, 3.1), and each second magnetisation vector extending parallel to the main faces (2.1, 3.1) and to a direction locally tangent to the element (2) provided with magnets, the width of each magnet (11, 12, 13, 14) being measured in a direction locally tangential to the element (2) in question.

5. Device according to claim 4, wherein the magnets (11, 12, 13, 14) have an angular sector shape and the first magnets (11, 13) have a radial dimension greater than a radial dimension of the second magnets (12, 14).

6. Device according to any one of the preceding claims, wherein the magnets (11, 12, 13, 14) are disposed according to a Halbach pattern.

7. Device according to any one of the preceding claims, wherein the magnets (11, 12, 13, 14) are carried by the stationary element (2).

8. Braked vehicle wheel (104) comprising a braking device according to any one of the preceding claims, comprising a rim, a wall or a hub to which the movable element (3) of the braking device is rotatably linked.

9. Landing gear (101) comprising a strut (102) having an end carrying a shaft (103), on which the hub of a wheel (104) is mounted according to claim 8, the stationary element (2) of the braking device being rotatably linked to the strut (102).