Eddy current magnetic braking device, braked vehicle wheel and aircraft landing gear equipped with such a wheel

Abstract

Eddy current magnetic braking device, comprising fixed (2) and mobile (3) elements having facing surfaces (2.1), 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. The plurality of magnets comprises first magnets (11, 13) having a first magnetization vector substantially perpendicular to the facing surfaces (2.1, 3.1) 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 first two magnets between which the second magnet is located. The magnets (11, 12, 13, 14) have widths 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.Aircraft wheel and landing gear incorporating such a device. ABSTRACT FIGURE: Fig. 3.

Description

Title of the invention: Eddy current magnetic braking device, braked vehicle wheel and aircraft landing gear equipped with such a wheel

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

[0002] BACKGROUND OF THE INVENTION

[0003] An aircraft wheel generally comprises a rim connected by a web to a hub mounted for rotation on a wheel support shaft (axle or spindle).

[0004] 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.

[0005] 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.

[0006] 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.

[0007] Document US-A-20200300310 also describes an eddy current magnetic braking device.

[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.

[0009] SUBJECT OF THE INVENTION

[0010] 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

[0011] To this end, according to the invention, there is provided an eddy current magnetic braking device, comprising two external elements framing a central element in relative motion with respect to the external elements, the external elements having first faces facing second opposite faces of the central element and each carrying a plurality of magnets capable of emitting via the first faces a magnetic flux generating in the central element, made of electrically conductive material, eddy currents when the elements are in relative motion, the magnets being arranged in such a way that the external elements attract each other.

[0012] This arrangement makes it possible to optimize and concentrate the magnetic flux and therefore to generate a surplus of eddy current, thus providing a relatively high braking torque greater than that which would be obtained with two assemblies consisting of a fixed element and a mobile element. With an adapted thickness of the central element, it is possible to obtain a “superposition of skin effects”. This is obtained with a thickness of the central element which is sufficiently low while satisfying the thermal and mechanical constraints.

[0013] The invention also relates to a braked wheel equipped with such a device and a landing gear equipped with such a wheel.

[0014] 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

[0015] Reference will be made to the accompanying drawings, among which:

[0016] [Fig.l] [Fig.l] is a partial schematic view of an aircraft equipped with a landing gear according to the invention;

[0017] [Fig.2] [Fig.2] is a partial schematic view of a wheel according to the invention, in axial section;

[0018] [Fig.3] [Fig.3] is a partial schematic view of a stator of a device of braking according to a first embodiment of the invention;

[0019] [Fig.4] [Fig.4] is a partial schematic view of a stator of a device of braking according to a second embodiment of the invention;

[0020] [Fig.5] [Fig.5] is a partial schematic view of a stator of a device of braking according to a third embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] With reference to Figures 1 and 2, 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 known manner, a hub 104 mounted to pivot on the shaft 102 and a rim 105 connected to the hub 104 by a web 106.

[0022] According to the invention, the wheels 103 are equipped with a magnetic braking device generally designated 1.

[0023] The magnetic braking device 1 comprises fixed elements, or stators 2, and mobile elements, or rotors 3.

[0024] 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 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.

[0025] The stators 2 are linked in rotation 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 linked in rotation 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.

[0026] 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.

[0027] The rotors 3 are made of copper or any other electrically conductive material.

[0028] Also with reference to figures 3 and 4, each stator 2 of each triplet 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.

[0029] 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 first two magnets 11, 13 between which the second magnet 12, 14 is located. 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. More precisely, the magnets 11, 12, 13, 14 have the shape of angular sectors and have a length L measured in a radial direction of the stator 2 and an average width 1 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 1 are measured in directions locally parallel to the facing surfaces (the main faces 2.1, 3.1).

[0030] 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 and so on... In this case:

[0031] - each magnet has its magnetization vector which comes out of 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.

[0032] It is understood that the magnets 12, 14 arranged on each side of the same magnet 11 have their magnetization vector oriented in opposite directions.

[0033] In each triplet, each magnet 11 of one of the two stators 2 faces a magnet 13 of the other of the two stators 2, and vice versa, so that all the magnets 11 face magnets 13 and attract each other through the rotor 3, which improves performance.

[0034] According to an advantageous version of the invention, the magnets 11, 12, 13, 14 have widths lu, l12, li3, lM such that the first magnets 11, 13 are spaced two by two by a first distance (equal to the width l12, lu) less than a second distance (equal to the width lu, ln) separating two by two the second magnets 12, 14. The best results are obtained when the width li2, li4 of the second magnets 12, 14 is approximately 70% of those - lu, li3 - of the first magnets 11, 13.

[0035] With reference to [Fig.3], the lengths Lu, L[2, Lu, Lu of the magnets 11, 12, 13, 14 are identical to each other.

[0036] With reference to [Fig.4], the lengths Lu, Ln of the magnets 11, 13 are identical to each other and the lengths Li2, Lu of the magnets 12, 14 are identical to each other. The lengths Lu, Ln of the magnets 11, 13 are greater than the lengths Li2, L 14 of the magnets 12, 14. Preferably, the length L12, L14 of the second magnets 12, 14 is approximately 70% of those - Lu, L13 - of the first magnets 11, 13.

[0037] In the arrangement shown in [Fig.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 South poles of the magnets 13.

[0038] It is understood that, in both embodiments, the magnets 12, 14 occupy a smaller surface area on the main face 2.1 than that of the magnets 11, 13.

[0039] 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 their support, the mass of which can be reduced since it does not need to provide a magnetic flux conduction function.

[0040] Both of the above embodiments allow an increase in the braking torque provided while limiting the mass and size of the device.

[0041] The first embodiment allows a higher braking torque than the second embodiment but on the other hand has a greater weight.

[0042] Each rotor 3 has a thickness such that a skin effect (otherwise called skin effect or Kelvin effect) is generated from each face 3.1 of the rotor 3 over more than half of the thickness of the rotor 3 at least over a range of possible relative speeds of the rotor 3 with respect to the stators 2. The eddy currents generated from the two faces 3.1 will then circulate in the central part of each rotor 3, which will increase the braking torque. This results in a “superposition of skin effects”, the thickness of the rotor 3 being sufficiently small to obtain this effect while satisfying the thermal and mechanical constraints. In one example, this effect gives approximately 60% more performance.

[0043] It is understood that to cause braking, the electromechanical control actuators are controlled to bring the stators 2 into the first position and that, to interrupt braking, the electromechanical control actuators are controlled 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 will then possibly be necessary to consider an additional brake.

[0044] 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 re- sales.

[0045] In particular, the device may have a structure different from that described.

[0046] The magnets can be carried by the rotor instead of the stator, two rotors framing a stator.

[0047] The shape, arrangement and dimensions of the magnets may be different from those described. For example, and according to the third embodiment shown in [Fig. 5], the magnets 11, 12, 13, 14 all have the same dimensions. Preferably, the first magnets 11, 13 will represent approximately 70% of the surface area of the element which carries them, but this is not obligatory.

[0048] The number of rotors and / or the number of stators may be different from those mentioned.

[0049] Although the rotor and the stator have been described in the form of parallel discs facing each other, the stator and the rotor can have other shapes. The device described is axial flux but the invention is applicable to operation in radial flux. Thus, the triplet can for example be arranged in the form of an outer drum and an inner drum between which extends a central drum in such a way that the central drum has an outer surface facing an inner surface of the outer drum and an inner surface facing an outer surface of the inner drum. The magnets are carried by the outer surface of the inner drum and by the inner surface of the outer drum.

[0050] 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.

[0051] Alternatively, the magnets may be directly attached to the rotor discs or stator discs of the friction brake, or the magnets may be covered with a friction lining, so that the braking device provides magnetic braking to slow the wheel when the discs are spaced apart from each other by an adequate air gap and friction braking when the discs are applied against each other. There is therefore no longer any axial stop between the discs in this embodiment.

[0052] It is possible to use, for the mechanical actuation of the magnetic braking device, an actuator acting on several stators sliding in the same direction. to be moved closer to the adjacent rotor, rather than one actuator for each stator.

[0053] Other modes of actuation of the magnetic brake are conceivable: for example electromagnetic by means of coils generating a magnetic field canceling that of the permanent magnets, rotors and stators being axially fixed.

[0054] The invention can be used on any type of vehicle.

Claims

Claims

1. Eddy current magnetic braking device, comprising two external elements (2) framing a central element (3) in relative motion with respect to the external elements (2), the external elements (2) having first faces (2.1) facing second opposite faces (3.1) of the central element (3) and each carrying a plurality of magnets (11, 12, 13, 14) capable of emitting via the first faces (2.1) a magnetic flux generating in the central element (3), made of electrically conductive material, eddy currents when the elements (2, 3) are in relative motion, the magnets being arranged in such a way that the external elements (2) attract each other, characterized in that the central element (3) has a thickness such that a skin effect is generated from each face (3.1) of the central element (3) over more than half of the thickness of the central element (3) at least over a range of possible relative speeds of the central element (3) with respect to the external elements (2).

2. Device according to claim 1, wherein the external elements (2) are stators and the central element (3) is a rotor.

3. A device according to claim 2, wherein the outer members (2) and the central member (3) are disc-shaped and have collinear central axes.

4. A device according to claim 1, wherein the plurality of magnets comprises first magnets (11, 13) and second magnets (12, 14) arranged alternately, the first magnets (11, 13) having a first magnetization vector substantially perpendicular to the facing surfaces (2.1, 3.1) and each of the second magnets (12, 14) having a second magnetization vector substantially perpendicular to the first magnetization vectors of the two first magnets between which it is located; and the magnets (11, 12, 13, 14) have widths 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.

5. A device according to claim 4, wherein the width of the second magnets (12, 14) is approximately 70% that of the first magnets (11, 13).

6. Device according to claim 4 or 5, in which the first magnets (11, 13) have a length measured in a direction perpendicular to their width and locally parallel to the facing 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 facing surfaces (2.1, 3.1).

7. Device according to claim 6, in which the length of the second magnets (12, 14) is approximately 70% that of the first magnets (11, 13).

8. Device according to claim 4, in which the first magnets (11, 13) represent approximately 70% of the surface (2.1) of the element (2) which carries them.

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

10. A device according to claim 9, 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).

11. A device according to any preceding claim, wherein the magnets (11, 12, 13, 14) are arranged in a Halbach pattern.

12. Device according to any one of the preceding claims, in which the magnets (11, 12, 13, 14) are carried by the fixed element (2).

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

14. Landing gear (101) comprising a leg (102) having one end carrying a shaft (103) on which is mounted the hub of a wheel (104) according to claim 13, the fixed element (2) of the braking device being rotationally linked to the leg (102).

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