Braking device with magnetized wedges

Abstract

The invention relates to a braking device comprising an armature, coils (7) received in slots (5) of the armature, and wedges (1) engaged in the slots (5) to at least partially close off the slots (5), each of the wedges (1) being composed of at least one material with permanent magnetization in a polarization direction. The invention also relates to an aircraft wheel (103) comprising such a braking device.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: Magnetic wedge braking device

[0003] The present invention relates to the field of braking devices and in particular to vehicle braked wheels.

[0004] BACKGROUND OF THE INVENTION

[0005] Braking devices are known to comprise at least one stator assembly and one rotor assembly. At least one of these assemblies includes an armature carrying copper coils (also called windings or coils) designed to generate a magnetic field from a current flowing through them or to allow the flow of a current induced by a magnetic field to which the coils are subjected. Each coil is generally made by winding an electrical conductor around a pole of the armature, each pole being laterally delimited by two adjacent slots in the armature parallel to the axis of rotation of the machine, which receive the turns of the electrical conductor forming the winding.

[0006] It is also known in the field of electrical machinery to close the slots, after the electrical conductor has been inserted, with shims positioned at their openings to protect the coils, prevent the intrusion of foreign objects into the slots, and possibly hold the coils in place. These shims are generally made of plastic or synthetic resin, materials that do not affect the magnetic fields induced or received by the coils. It is also known to use shims made of non-magnetic magnetic materials to avoid disturbing the magnetic fields.

[0007] OBJECT OF THE INVENTION The invention aims in particular to improve the performance of a braking device.

[0008] SUMMARY OF THE INVENTION

[0009] For this purpose, according to the invention, a braking device is provided comprising an armature, coils received in slots of the armature, and wedges engaged in the slots to at least partially close the slots, each of the wedges is composed of at least one material with permanent magnetization along a polarization direction.

[0010] Thus, the magnetic shims are arranged to enhance the magnetic flux produced by the coils, for example by concentrating it, and to optimize the distribution of magnetic fields acting within the braking system during operation. The magnetic shims improve the energy efficiency of the braking system and therefore its performance, without altering the structure of the braking system.

[0011] Depending on optional features, used individually or in whole or in combination:

[0012] - the wedges and energized coils are arranged with magnetization directions oriented to form a Halbach lattice; the material of the wedges has resistance to temperatures at least equal to a maximum operating temperature of the coils; the wedges have hardness characteristics facilitating their placement and retention in the slots; the wedges include an outer coating having a hardness greater than that of the permanently magnetized material; the wedges are formed by assembling sections; the armature forms a rotor of the device; the armature forms a stator of the device.

[0013] The invention also relates to a wheel equipped with a braking device according to the invention.

[0014] Other features and advantages of the invention will become apparent from the following description of a particular and non-limiting embodiment of the invention.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Reference will be made to the attached drawings, including:

[0017] [Fig. 1] is a general view of an aircraft equipped with braked wheels according to the invention;

[0018] [Fig. 2] is a schematic cross-sectional view of an aircraft wheel equipped with an electromagnetic braking device according to the invention;

[0019] [Fig. 3] is a cross-sectional view of a rotor armature of a braking device according to a first embodiment of the invention;

[0020] [Fig. 4] is a schematic perspective view of one of the magnetized magnetic wedges that equip this rotor armature;

[0021] [Fig. 5] is a diagram showing the orientation of the magnetization vectors of a series of adjacent magnetized wedges and alternating coils;

[0022] [Fig. 6] is a schematic representation of the magnetic field lines in this rotor armature;

[0023] [Fig. 7] is a schematic perspective view of the magnetic wedges according to one embodiment variant;

[0024] [Fig. 8] is a partial schematic, perspective view of a stator armature of a braking device according to a second embodiment;

[0025] [Fig. 9] is a partial schematic view of the braking device according to the second embodiment.

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027] With reference to Figures 1 and 2, the invention is described herein in application to an aircraft 100 comprising landing gear 101, each having a leg with 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. Each wheel 103 comprises a rim 103.1 carrying a tire 103.2, a hub 103.3 extending coaxially with 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.

[0028] Each wheel 103 is equipped with an electromagnetic braking device 2, here housed in the annular space 103.5. The braking device 2 comprises a stator armature 3 and a rotor armature 4. The stator armature 3 is rotationally connected to the axle 102, while the rotor armature 4 is rotationally connected to at least one element of the wheel 103, here the hub 103.3. The stator armature 3 and the rotor armature 4 have annular shapes. According to the embodiments:

[0029] - the rotor armature 4 is housed in the stator armature 3 so as to have an external surface, of cylindrical shape, opposite an internal surface, of cylindrical shape, of the stator armature 3;

[0030] - the stator armature 3 is housed in the rotor armature 4 so as to have an external surface, of cylindrical shape, facing an internal surface, of cylindrical shape, of the rotor armature 4.

[0031] One end of the stator and rotor is made of electrically conductive material, while the other end is equipped with electromagnets to produce an electromagnetic flux towards the electrically conductive material. When the rotor and stator are in relative motion, this magnetic flux induces eddy currents in the electrically conductive material, which in turn produce a braking torque to counteract the relative motion.

[0032] In the first embodiment, and with reference to figures 3 to 6, the rotor armature 4 comprises a central annular body 4.1, centered on the X axis, and teeth 6 which extend radially outwards from the central annular body 4.1 and which are separated from each other by slots 5 opening onto the external surface 4.2 of the rotor armature 4. The slots 5 extend parallel to the X axis and are regularly angularly distributed around the X axis.

[0033] All 5 slots are identical and have a mouthpiece

[0034] 5.1 opposite the internal surface of the stator armature 3. Each slot 5 has, in the vicinity of the central annular body 4.1, a bottom 5.2 wider than the width of the mouth 5.1. This is due to the fact that the teeth 6 are essentially T-shaped, each with a base

[0035] 6.1 relatively narrow in the vicinity of the central annular body 4.1 and a head 6.2 relatively wide forming the external surface 4.2 of the rotor armature 4.

[0036] The rotor armature 4.1 is provided with coils 7 wound around the teeth 6 under the heads 6.2. The head 6.2 of the teeth 6 allows the coils 7 to be held in position by preventing them from sliding along the teeth 6 and separating from the rotor armature 4. The coils are supplied in a conventional manner, for example by brushes.

[0037] Each tooth 6 is thus surrounded by a coil 7, and when a current is sent through the coil, a magnetic field is induced. This induced magnetic field has a direction and a sense. Since the windings of the coils 7 are positioned around the teeth 6, which extend radially around the rotor armature, the direction of the induced field is therefore radial to the rotor armature. The direction of the field, in turn, is determined by the direction of the current flowing through the coil. The direction of the induced magnetic field is thus determined during the winding and connection process. Between each of the teeth 6, a spacer 1 is placed to hold and protect the coils 7 extending into the slots 5. Each spacer 1 therefore closes the opening of one of the slots 5.

[0038] The wedges 1 are bar-shaped and have two main faces, a first main face 1.1 facing outwards from the slot and a second main bottom face 1.2 facing towards the bottom of the slot 5, as well as a first secondary lateral face 1.3 and a second secondary lateral face 1.4 connecting the main faces 1.1,

[0039] 1.2 to each other. The two secondary lateral faces

[0040] 1.3 and 1.4 bear against the teeth 6 of the rotor body 4.1 and have a profile that fits the heads 6.2 of said teeth 6. A chamfer 1.5 is present on these secondary lateral faces 1.3 and 1.4 to coincide with a chamfer shape present at the heads 6.2 of the teeth 6. Each of these shims 1 is composed of a permanently magnetized material that induces a magnetic field around it. Thus, each shim 1 is a permanent magnet with two poles inducing a magnetic field around itself from one pole to the other.

[0041] Each of the wedges is arranged in one of the slots 5 of the rotor armature 4 according to a particular magnetization vector orientation, such that the set of wedges 1 and the set of energized coils 7 form a Halbach pattern. For this purpose, with reference to Figure 8, the wedges 1 and the teeth 6 equipped with coils 7 are arranged in successive series of wedges 1 and coils 7 such that the first lateral surface 1.3 and the second lateral surface 1.4 of each wedge 1 are adjacent to a tooth 6 equipped with a coil 7. The wedges 1 and the coils 7 are arranged in each series such that each series includes a first coil 7A generating a magnetic field going from the inside of the rotor armature to the outside, a first wedge 1B, adjacent to this first coil 7A, having a magnetic field going from the first secondary lateral face 1.3 to the second secondary lateral face 1.4, a second coil 7C adjacent to the first wedge 1B generating a magnetic field going from the outside of the rotor armature towards the inside, and a second wedge 1D, adjacent to the second coil 7C, generating a field going from the second secondary lateral face 1. towards the first secondary lateral face 1.3. It is understood that:.

[0042] - the 7A coils, when energized, therefore have a magnetization vector extending radially along the X axis from the inside of the rotor armature outwards;

[0043] - the 1B wedges have a magnetization vector extending from the first secondary lateral face 1.3 to the second secondary lateral face 1.4;

[0044] - the 7C coils, when energized, have a magnetization vector extending radially to the X axis from the outside of the rotor armature outwards;

[0045] - the 1D wedges have a magnetization vector extending from the second lateral secondary face 1.4 to the first lateral secondary face 1.3.

[0046] In this configuration, the Halbach pattern amplifies the magnetic field strength on the side of the first principal faces 1.1 and reduces the magnetic field strength on the side of the second principal faces 1.2 (see the field lines symbolized in Figure 6). The concentration of the magnetic flux outwards from the rotor assembly 4, and therefore towards the stator armature 3, is responsible for optimizing the performance of the magnetic braking device 2, particularly its torque characteristic.

[0047] The shims 1 are monolithic and cut from a bar of ferromagnetic or permanently magnetized ferrimagnetic material, possessing temperature resistance characteristics sufficient to withstand the maximum operating temperatures of the electromagnetic braking device 2, and more particularly the maximum temperature reached by the coils in operation. In particular, the material in question has a Curie temperature higher than the maximum operating temperature encountered in the machine.

[0048] The material composing the wedges 1 also possesses mechanical resistance characteristics enabling the wedges 1 to withstand the maximum forces attainable during the operation of the electromagnetic braking device 2. In addition, the material has a hardness that facilitates the placement of the wedges 1 and their retention in the slots 5 during the operation of the brake.

[0049] According to a first variant, the wedges 1 include an outer coating having advantageous characteristics to reinforce and protect said wedges 1. This coating has, for example, a hardness greater than that of the magnetic material which makes up the wedges 1.

[0050] According to a second variant, shown in Figure 7, each of the wedges 1 is an assembly of several sections joined lengthwise along the wedge 1. The sections here have a very small thickness. More precisely, the wedge 1 is laminated, that is, it is formed by assembling sheets. This assembled structure notably reduces hysteresis losses. According to a second embodiment shown in Figures 8 and 9, it is the stator armature 3 that comprises teeth laterally delimited by slots that receive coils and are closed by wedges 1 made of magnetized material.

[0051] Just like the rotor assembly 4 of the first embodiment, the teeth 6 have a general T-shape and each tooth is surrounded by a coil 7. The slots 5 are also closed and protected by the positioning of the same wedges 1 made of magnetized magnetic material. In this second embodiment, the openings of the slots 5 face the interior of the stator assembly 3, that is, towards the rotor assembly 4.

[0052] The wedges 1 and the coils 7 supplied with current also form, by the orientation of their magnetization vector, a Halbach lattice so as to increase the intensity of the magnetic field in the direction of the interior of the stator armature 3, that is to say in the direction of the rotor armature 4.

[0053] This second embodiment is interesting because it allows the mass of the rotor to be limited and facilitates the supply of power to the coils.

[0054] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0055] In particular, the shape of wedge 1 is described as having a chamfer. However, the geometry of the wedge depends on the geometry of the space intended to receive the wedges, so the presence of a chamfer is not mandatory.

[0056] Although the sections shown in Figure 7 are shown in a direction perpendicular to the length of the wedge, it is possible that the cutting of the sections is carried out in another direction, such as parallel to the length of the wedge for example.

[0057] Although in each of the embodiments shown here the rotor armature is central and surrounded by a stator armature, it is possible for the stator armature to be central and surrounded by the rotor armature. Even though the arrangement of the magnetized wedges 1 and the coils 7 in a Halbach lattice allows for amplifying the magnetic fields produced and increasing the performance of the braking device, this arrangement is not mandatory.

[0058] The invention is applicable to any type of axial or radial flow braking device...

Claims

DEMANDS 1. Braking device comprising an armature, coils (7) received in slots (5) of the armature, and wedges (1) engaged in the slots (5) to at least partially close the slots (5); characterized in that each of the wedges (1) is composed of at least one material with permanent magnetization along a polarization direction.

2. Device according to claim 1, wherein the wedges (1) and the energized coils (7) are arranged with magnetization directions oriented to form a Halbach grating.

3. Device according to any one of the preceding claims, wherein the material of the wedges (1) exhibits resistance to temperatures at least equal to a maximum operating temperature of the coils (7).

4. Device according to any one of the preceding claims, wherein the wedges (1) have hardness characteristics facilitating their placement and retention in the slots (5).

5. Device according to claim 4, wherein the wedges (1) comprise an outer coating having a hardness greater than that of the permanently magnetized material.

6. Device according to any one of the preceding claims, wherein the wedges (1) are formed by assembling sections.

7. Device according to any one of the preceding claims, wherein the armature (3) forms a rotor of the device.

8. Device according to any one of claims 1 to 6, wherein the armature (4) forms a stator of the device.

9. Aircraft wheel (103) comprising a device according to any one of the preceding claims.

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