Controllable magnetic braking device with permanent magnets

Abstract

Eddy current magnetic braking device, comprising at least a first element and a second element movable relative to each other with facing surfaces, the first element being electrically conductive and the second element being provided with a magnetic array comprising permanent magnets to produce a magnetic field between the facing surfaces and induce an eddy current in the first element, the permanent magnets of the magnetic array comprising at least first magnets carried by a first support and second magnets carried by a second support movable relative to the first support between an activated brake position in which the field of the second magnets is added to the field of the first magnets and a deactivated brake position in which the field of the second magnets is subtracted from the field of the first magnets,the device comprising at least one actuator to move the second support between its two positions. FIGURE IN ABRIDGED DIAGRAM: Fig. 1,

Description

Title of the invention: Controllable magnetic braking device with permanent magnets

[0001] The present invention relates to the field of eddy current braking.

[0002] BACKGROUND OF THE INVENTION

[0003] Eddy current braking devices are known, comprising electromagnets that control the induction of an eddy current in a braked element to generate a braking torque for said element. The electromagnet, with its limited volume and low mass, controls the generation of a magnetic field. However, the intensity of the magnetic field generated by these electromagnets is limited and insufficient in certain applications.

[0004] Eddy current magnetic braking devices using permanent magnets are also commonly encountered. This type of magnet makes it possible to provide magnetic field strengths much higher than those produced by electromagnets. Since these permanent magnets cannot be switched on or off, it is known to physically move these magnets by bringing them closer to or further from the elements to be braked, in order to amplify or reduce the eddy current induced in said element. This solution is more cumbersome than the electromagnet solution. Furthermore, this solution leaves a risk of residual braking due to the still-active magnetic fields, which can cause significant energy losses.

[0005] SUBJECT OF THE INVENTION

[0006] The invention aims in particular to provide a permanent magnet eddy current braking solution that makes it possible to remedy at least in part the aforementioned disadvantages. Summary of the invention

[0007] To this end, the invention provides a magnetic eddy current braking device comprising at least a first element and a second element movable relative to each other with facing surfaces, the first element being electrically conductive and the second element being provided with a magnetic array comprising permanent magnets to produce a magnetic field between the facing surfaces and induce an eddy current in the first element. The permanent magnets of the magnetic array comprise at least first magnets carried by a first support and second magnets carried by a second support movable relative to the first support between a braking position activated in which the field of the second magnets is added to the field of the first magnets and a deactivated brake position in which the field of the second magnets is subtracted from the field of the first magnets, the device comprising at least one actuator to move the second support between its two positions.

[0008] Thus, in the device of the invention, the permanent magnets are carried by supports that are movable relative to each other between an activated brake position and a deactivated brake position. The movement of these supports allows either an addition of the magnetic fields generated by the magnets to apply a significant braking torque, or a compensation of the fields of the different magnets to reduce the braking torque as much as possible. The invention thus makes it possible to provide a vehicle with powerful eddy current magnetic braking, since it uses permanent magnets, while limiting the resulting mass and size.

[0009] The invention also relates to a vehicle, such as an aircraft, equipped with such a braking device.

[0010] Other features and advantages of the invention will become apparent from the following description of particular, non-limiting embodiments of the invention. Brief description of the drawings

[0011] Reference will be made to the attached drawings, among which:

[0012] [Fig-1] is a front view of an aircraft having landers equipped with a braking device according to the invention;

[0013] [Fig.2] is a cross-sectional view of a braking device according to a first embodiment of the invention;

[0014] [Fig.3] is a diagram illustrating the magnetic field lines generated by a pair of magnets when the magnetic network is, respectively, in an activated brake position and in a deactivated brake position;

[0015] [Fig.4] is a perspective view of the magnetic network, in the activated brake position, the braking device being mounted on an axle;

[0016] [Fig.5] is a view analogous to [Fig.4] of the magnetic network in the deactivated brake position;

[0017] [Fig.6] is a perspective view showing a wheel equipped with the braking device according to the first embodiment;

[0018] [Fig.7] is a cross-sectional view of a braking device according to a second embodiment;

[0019] [Fig.8] is a cross-sectional view of a braking device according to a third embodiment;

[0020] [Fig.9] is a cross-sectional view of a braking device according to a fourth embodiment;

[0021] [Fig. 10] is a perspective view of the braking device according to the fourth embodiment;

[0022] [Fig. 11] is a schematic representation of the Halbach pattern formed by the positioning of the magnets in the supports of a braking device according to a fifth embodiment;

[0023] [Fig. 12] is a schematic view illustrating bars of a braking device according to a sixth embodiment;

[0024] [Fig. 13] is a diagram illustrating the lines of the magnetic fields generated by a pair of magnets equipped with a ferromagnetic bar according to the sixth embodiment;

[0025] [Fig. 14] is a schematic view illustrating ferromagnetic bars split in two according to a variant of the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] With reference to [Fig. 1], the invention is here described in application to an aircraft 1000 comprising landers 101 each having a leg having an end provided with at least one axle 102 on which is mounted, pivoting about an axis X of rotation, at least one braked wheel 103.

[0027] With reference to figures 2 to 6 and according to the first embodiment, each wheel 103 comprises a rim 103.1 carrying a tire 103.2, a hub 103.3 extending coaxially to the rim 103.1 defining with it an annular space 103.5, and a disc 103.4 connecting the hub 103.3 to the rim 103.1. Around the axle is positioned coaxially therewith, a torsion tube 104 linked to the leg of the lander 101.

[0028] Each wheel 103 is equipped with an electromagnetic braking device 100 comprising a first element 1 and a second element 2 that rotate relative to each other. One of these two elements, the rotor, is rotationally connected to the wheel 103 and the other, the stator, is connected to the torsion tube 104.

[0029] According to a first embodiment, the rotor is an electrically conductive element 1 of substantially annular shape, comprising two main flat surfaces 1.1 and 1.2 (transverse to the X axis) as well as an outer periphery 1.3 and an inner periphery 1.4. The rotational connection of the electrically conductive element 1 to the rim 103.1 of the wheel 103 is ensured by screws 3 engaged axially in a front face of the rim 103.1 by passing through a collar which extends radially from the outer periphery 1.3 of the electrically conductive element 1 which bears against said front face of the rim 103.1. The electrically conductive element 1 thus extends to the entrance of the annular space 103.5.

[0030] The second element comprises a magnetic array 2, substantially annular in shape, which includes two main plane surfaces 2.1 and 2.2, and which is rotationally connected to the axle 102 of the aircraft 1000 by the torsion tube 104 and the landing gear leg. More specifically, the magnetic array 2 is centered on the X-axis and fixed to the torsion tube 104 by means of screws 3. The main surface 2.1 of the magnetic array 2 extends opposite the main surface 1.1 of the electrically conductive element 1.

[0031] The magnetic network 2 has two supports 4, each of these supports 4 carrying a set of permanent magnets 5.

[0032] The set of self-magnetic fields forms a general magnetic field.

[0033] The supports 4 are annular in shape, and the magnets 5 are fixed in a ring to the supports. An inner support 4.1 and an outer support 4.2 are distinguished, each having an inner and an outer diameter, the inner support 4.1 having an outer diameter smaller than the inner diameter of the outer support 4.2. The inner support 4.1 is then positioned inside the outer support 4.2, on the same plane. The magnetic array 2 thus has an inner perimeter 2.3 and an outer perimeter 2.4. The supports 4 are mounted relative to each other so as to be free to rotate about the X-axis.

[0034] The internal support 4.1 comprises a flange extending inwards radially from the inner periphery 2.3, along the plane of one of the principal surfaces of the magnetic array 2, and the internal support 4.1 is connected to the torsion tube 104 by tightening screws 3 screwed into the torsion tube 104 through said flange. The screws 3 are then positioned parallel to the X-axis.

[0035] The external support 4.2 is itself mobile in rotation about the X-axis around the internal support 4.1. The rotational drive of the external support 4.2 is ensured by linear actuators 6 extending from the side of the main face 2.2 and each having a first end 6.1 pivotally mounted on a main face of the external support 4.2 and a second end 6.1 pivotally mounted on a main face of the internal support 4.1. The linear actuators 6 are arranged to apply a movement of approaching or separating the two pivots to which they are connected, one of the two pivots being fixed to the external support 4.2 and the other of the two pivots being fixed to the internal support 4.1, thus allowing the rotational movement of the external support 4.2 relative to the internal support 4.1 linked to the axle 102.

[0036] The actuators 6 have a variable length within a range suitable for rotating the external support 4.2 relative to the internal support 4.1 along the X axis between two positions, one of these two positions corresponding to an activated brake position and the other of these two positions corresponding to a deactivated brake position.

[0037] The magnets 5 carried by the supports 4 of the magnetic network 2 are arranged to produce a magnetic field having a direction (we speak of the direction of magnetization) and a sense on this direction which will now be specified.

[0038] All the magnets 5 have a crown-like shape and are adjacent in pairs by lateral end faces, the set of magnets 5 adjacent in pairs thus form substantially a crown.

[0039] In this first embodiment, the magnets 5 are arranged to each produce their own magnetic field whose direction is parallel to the X axis.

[0040] It is recalled that the main function of this magnetic network 2 is to produce a magnetic field inducing eddy currents in the electrically conductive element 1. The general magnetic field produced therefore comprises field lines extending at the level of the main surfaces 2.1 and 1.1 of the magnetic network 2 and the electrically conductive element 1 facing each other, and passing through the electrically conductive element 1. The eddy current induced in the electrically conductive element 1 linked to the wheel 103 makes it possible to apply a magnetic resistance to its movement, this then results in the application of a resistive torque opposing the rotation of the wheel 103, in other words the braking of said wheel 103.

[0041] The invention makes it possible to modify the magnetic field produced and therefore the braking torque.

[0042] In the first embodiment, the magnets 5 of each support 4 are positioned according to a repeating pattern of two adjacent magnets 5, comprising one magnet 5 rotated in a first direction and one magnet 5 rotated in a second direction opposite to the first, such that the two magnets 5 of the same pattern produce magnetic fields in opposite directions. This repeating pattern of two magnets 5 in opposite directions requires an even number of magnets 5 for each support 4.

[0043] It is understood that the self-magnetic fields of the magnets 5 of each support 4 are impacted by the self-magnetic fields of the nearby magnets 5, that is to say the adjacent magnets 5 carried by the same support 4, as well as the nearby magnets 5 carried by the other support 4.

[0044] In each of the two positions of the external support 4.2 (brake activated and brake deactivated), each magnet 5 of the internal support 4.1 is aligned, along a radial direction perpendicular to the X axis, with a magnet 5 of the external support 4.2. These groups of two aligned magnets 5 are then called "pairs of magnets".

[0045] With reference to Figures 3 and 4, when the magnetic array 2 is in its activated brake position, the pairs of magnets 5 comprise two magnets 5 having two magnetic fields having the same direction and sense. Thus, the fields the self-magnetics of the two magnets 5 add up and the lines of the field thus amplified are directed outwards from the magnetic lattice 2.

[0046] With reference to Figures 3 and 5, when the external support 4.2 is in its deactivated brake position, the pairs of magnets 5 comprise two magnets 5 having two magnetic fields having the same direction but opposite senses. Thus, the self-magnetic fields of the two magnets 5 cancel each other out, and the path of the field lines is short-circuited from a surface of one magnet of one pair of magnets 5 to a surface of the other magnet of said pair.

[0047] The general magnetic field results from the addition of all these magnetic fields of pairs of magnets 5 influencing each other.

[0048] Thus, it is when the magnetic network 2 is in its activated braking position that the overall magnetic field generated passing through the electrically conductive element 1 has a maximum intensity, and that the eddy currents induced in said electrically conductive element 1 are the greatest. Consequently, it is in this configuration that the braking device 100 applies the greatest braking torque to the wheel 103.

[0049] Concurrently, it is when the magnetic network 2 is in its deactivated braking position that the overall magnetic field generated passing through the electrically conductive element 1 has its lowest intensity, and that the eddy currents induced in said electrically conductive element 1 are the lowest. Consequently, it is in this configuration that the braking device 100 applies the least braking torque to the wheel 103. In this configuration, the braking torque can be considered negligible, and the brakes are thus considered disengaged.

[0050] With reference to [Fig. 7] and according to a second embodiment, the braking device 100 comprises all the elements of the first embodiment, and additionally comprises a second magnetic network 2' similar to the first. This second magnetic network 2' is arranged to also have a principal surface opposite the principal surface 1.2 of the electrically conductive element 1. The internal support of the second magnetic network 2' is connected and screwed to the same torsion tube 104 as the internal support 4.1 of the first magnetic network 2.

[0051] In this configuration, the two magnetic networks 2 and 2' are positioned on either side of the electrically conductive element 1, and are both arranged to be able to simultaneously induce eddy currents in said electrically conductive element 1.

[0052] This configuration makes it possible to induce eddy currents of greater intensity than in the first embodiment, and thus to produce a much more effective braking.

[0053] With reference to [Fig. 8] and according to a third embodiment, several additional electrically conductive elements 1'' are rotationally linked to the wheel about the X-axis and are positioned side-by-side in the annular space 103.5 of the wheel 103. Near each of these additional electrically conductive elements 1'' are additional magnetic arrays 2'', each having at least one face opposite a face of the electrically conductive element 1'', and being capable of inducing eddy currents in that element. These magnetic arrays 2'' may be one per electrically conductive element 1'', as shown in the first embodiment, or two, as described in the second embodiment. It is envisaged that, in the configuration comprising two magnetic arrays 2'' per electrically conductive element 1'', two magnetic arrays 2'' will be placed side-by-side.In this case, an actuator 6 can be arranged so that one of its ends is connected simultaneously to the two external supports 4.2 of these two magnetic networks 2” and the other of its ends is connected to the two internal supports 4.1 of these same two magnetic networks, thus allowing an actuator 6 to apply a movement to the supports 4 of the two magnetic networks 2’’ simultaneously.

[0054] With reference to figures 9 and 10, according to a fourth embodiment, the braking device comprises the same components as described in the first embodiment, however, the structure of the electrically conductive element 1'" and the magnetic network 2'' differs from the other embodiments.

[0055] Indeed, whereas in the previous embodiments the magnets 5 are positioned to produce an axial magnetic flux (i.e. parallel to the X-axis), the magnets 5 are positioned in the fourth embodiment to produce a radial magnetic flux (i.e. perpendicular to the X-axis). As a result, the two elements 1, 2 are annular but are engaged with each other.

[0056] Here, the magnetic lattice 2''' has an external diameter smaller than the internal diameter of the electrically conductive element 1”'. Thus, the surfaces opposite these two elements through which the magnetic fields pass are the external and internal cylindrical surfaces respectively of the magnetic lattice 2'' and the electrically conductive element 1 ”'.

[0057] In this fourth embodiment, within the magnetic network 2, the two supports 4 are annular in shape and of the same diameter. They are positioned coaxially with the X-axis and are juxtaposed with respect to each other. The magnets 5 are fixed to the supports 4 so as to have a magnetic field direction extending radially, that is, perpendicularly to the X-axis. On each of the supports, the magnets are positioned to form a ring around the X-axis and such that the directions of their own magnetic fields alternate, one magnet 5 producing a magnetic field in a direction radially towards the X-axis is located between two magnets 5 producing a magnetic field in a direction radially opposite to the X-axis. As before, one of the supports 4, here support 4.2, is mounted to pivot about the X-axis relative to the other support, here support 4.1, such that the magnets 5 of support 4.1 and the magnets 5 of support 4.2 can be aligned (the magnets 5 of support 4.1 producing a magnetic field in the direction radially towards the X-axis are aligned along the X-axis with the magnets 5 of support 4.1 producing a magnetic field in the direction radially towards the X-axis) or offset (the magnets 5 of support 4.1 producing a magnetic field in the direction radially towards the X-axis are aligned along the X-axis with the magnets 5 of support 4.1 producing a magnetic field in the direction opposite to the X-axis) according to the X axis by rotation of support 4.2 relative to support 4.1.

[0058] With reference to [Fig. 11], and according to a fifth embodiment, the architecture of the elements is similar to any of the preceding embodiments, but the magnets 5 are arranged according to a so-called Halbach pattern.

[0059] More specifically, the arrangement of the magnets 5 is a repetition of a pattern of four magnets: - a first magnet having a magnetic field whose direction is radial with respect to the X axis and whose direction is directed towards the X axis; - a second magnet having a magnetic field in a first direction along a direction perpendicular to the X axis and to the radial direction; - a third magnet having a magnetic field whose direction is radial with respect to the X axis and whose direction is directed in the opposite direction to the X axis; - a fourth magnet having a magnetic field in a second direction opposite to the first direction along the direction perpendicular to the X axis and to the radial direction.

[0060] In the sixth embodiment illustrated in Figures 12 and 13, the braking device has a structure similar to that of the first embodiment and comprises metal bars 7 extending radially across the supports 4.1, 4.2 such that, when the magnetic network 2 is in its deactivated braking position, each bar 7 extends opposite a magnet 5 of the support 4.1 and the adjacent magnet 5 carried by the support 4.2 to close the magnetic field produced by these magnets 5 before the electrically conductive element 1. The magnetic field thus does not risk generating eddy currents in the electrically conductive element 1.

[0061] This metal bar comprises a ferromagnetic material capable of concentrating and guiding field lines.

[0062] The bar 7 comprises two sections 7.1 and 7.2, each of which is positioned opposite one of the two faces of each pair of magnets 5 from which the magnetic fields emerge. Each bar 7 can be either fixed to one of the supports, or fixed to one of the magnets, or fixed to a frame independent of the supports so as to allow movement of the two supports 4 of the magnetic lattice 2 relative to each other.

[0063] With reference to figures 12 and 13, the section 7.1 of each bar 7 is fixed to one of the faces of one of the magnets 5 of the support 4.1.

[0064] With reference to [Fig.14], it is also envisaged that the sections 7.1, 7.2 of each bar 7 can be separated from each other and fixed for the first on one of the magnets 5 of the support 4.1 and for the second on one of the magnets 5 of the support 4.2.

[0065] Regardless of the arrangement of the bars 7, the bars 7 are arranged so as: - not to hinder the propagation of the magnetic field produced when the magnetic network 2 is in the activated brake position (thus, they do not cover all the magnets but only a portion of them), and - to promote the looping of field lines when the magnetic network is in the deactivated braking position. This helps to reduce the risk of residual braking.

[0066] 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.

[0067] In particular, although here the electrically conductive element 1 is rotationally linked to the wheel 103, and the magnetic network 2 and the actuators 6 are rotationally linked to the torsion tube 104 and the axle 102, it is possible that the magnetic network 2 and the actuators 6 are rotationally linked to the wheel 103 and that the electrically conductive element 1 is rotationally linked to the torsion tube 104 and the axle 102.

[0068] Although here the lander 101 includes an axle 103 on which two wheels are mounted, it is possible that the lander 101 may be of another shape with another number of wheels 103, such as for example a half axle on which a single wheel 103 is mounted.

[0069] The first element and the second element form a braking module and the device may include one or more braking modules.

Claims

Demands

1. Eddy current magnetic braking device (100), comprising at least a first element (1) and a second element (2) movable relative to each other with facing surfaces (1.1, 2.1), the first element being electrically conductive and the second element being provided with a magnetic array comprising permanent magnets (5) to produce a magnetic field between the facing surfaces and induce an eddy current in the first element, characterized in that the permanent magnets of the magnetic array (2) comprise at least first magnets (2.1) carried by a first support (4.1) and second magnets carried by a second support (4.2) movable relative to the first support between an activated brake position in which the field of the second magnets adds to the field of the first magnets and a deactivated brake position in which the field of the second magnets subtracts from the field of the first magnets, the device comprising at least one actuator (6) for moving the second support between its two positions.

2. Braking device according to claim 1, wherein the second element (2) and the first element (1) are rotationally movable relative to each other about an axis of rotation (X) on which the facing surfaces are centered, and wherein the second support (4.2) is rotationally movable relative to the first support (4.1) about this same axis of rotation.

3. Braking device according to claim 2, wherein the supports (4.1, 4.2) are rings coaxial with each other.

4. Braking device according to any one of claims 2 and 3, wherein the magnetic field produced by the magnetic network (2) is directed parallel to the axis of rotation (X), and wherein the supports (4.1, 4.2) are of different diameters and are on the same plane.

5. Braking device according to any one of claims 2 and 3, wherein the permanent magnets (5) are arranged on the supports (4.1, 4.2) in such a way that the magnetic field produced by the magnetic network (2) is directed radially with respect to the axis of rotation (X), the two supports (4.1, 4.2) being substantially of the same diameter and juxtaposed to each other.

6. Braking device according to any one of the preceding claims, wherein the permanent magnets (5) within the magnetic network (2) are arranged in such a way that two permanent magnets (5) of the same support (4.1, 4.2), adjacent to each other, produce magnetic fields each in a direction normal to the facing surfaces and in opposite directions.

7. Braking device according to any one of the preceding claims, wherein the permanent magnets (5) carried by the same support (4.1, 4.2) are arranged according to a Halbach pattern.

8. Braking device according to any one of the preceding claims, comprising metallic bars (7) positioned against two magnets (5) to loop the magnetic fields produced by said permanent magnets (5) when the second support (4.2) is in the deactivated brake position.

9. Braking device according to any one of the preceding claims, wherein said device comprises two second elements (2) positioned on either side of the first element (1), arranged to each induce an eddy current in said first element (1).

10. Braking device according to any one of the preceding claims, wherein the first element (1) and the second element (2) form a braking module and the device comprises several braking modules.

11. A vehicle wheel comprising a rotating shaft and a braking device according to any one of the preceding claims, wherein one of the first elements (1) is rotationally linked to the wheel and one of the second elements (2) is rotationally linked to the shaft

12. Aircraft comprising at least one landing gear having at least one wheel according to claim 11.