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

Abstract

Eddy current magnetic braking device (1), comprising a stator (2) and a rotor (3), one of which carries a plurality of permanent magnets (10.1, 10.2) to emit towards the other a first radial magnetic flux capable of generating eddy currents when the stator and the rotor are engaged in each other in a maximum braking position, the stator (2) and the rotor (3) being movable relative to each other between the maximum braking position and a free rotation position in which they are at least partially disengaged from each other. One of the stator and rotor comprises two active parts (2.1, 2.2) for the production of eddy currents which are axially mobile relative to each other to be brought closer together when the stator (2) and the rotor (3) are in the maximum braking position and moved apart when the stator (2) and the rotor (3) are in the free rotation position.Vehicle wheel, aircraft landing gear and aircraft incorporating such a device. FIGURE IN ABRIDGED: Fig. 3.

Description

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

[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 mounted opposite an electromagnetic stator.

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

[0008] The operating principle is always the same. The magnetic braking device comprises a rotor rotatably connected to the wheel and a stator mounted opposite the rotor. One of the rotor and the stator is made of electrically conductive material and the other of the rotor and the stator is provided with magnets producing a magnetic field which gives rise, when the rotor pivots opposite the stator, to eddy currents generating a braking torque opposing the pivoting of the rotor. This braking torque depends on the power of the magnets and the air gap separating the rotor and the stator. Conventionally, the braking device is controlled by varying this air gap by a relative movement of the rotor and the stator between a maximum braking position in which the stator and the rotor are as close as possible to each other and a minimum braking position in which the stator and the rotor are far from each other. the other. It is understood that the amplitude of the air gap variation conditions the size of the braking device and that the more quickly this air gap variation can be carried out, the more responsive the control of the braking device can be.

[0009] There are radial flux braking devices in which the rotor and the stator have the shape of drums, namely an external drum and an internal drum movable relative to each other between a position in which the internal drum is received in the external drum - the air gap then being minimal and the braking torque maximum - and a position in which the internal drum is disengaged from the external drum - the air gap then being maximal and the braking torque minimal.The extent of the relative displacement of the inner drum and the outer drum determines the axial size of the braking device and the stroke of the actuator or actuators responsible for this relative displacement, which also has consequences on the mass of the braking device. However, mass and size are severe constraints for use in the transport sector and in particular on aircraft.

[0010] SUBJECT OF THE INVENTION

[0011] 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

[0012] To this end, according to the invention, there is provided an eddy current magnetic braking device, comprising a stator and a rotor, one of which carries a plurality of permanent magnets for emitting towards the other a first radial magnetic flux capable of generating eddy currents when the stator and the rotor are engaged in one another in a maximum braking position, the stator and the rotor being movable relative to one another between a maximum braking position and a free rotation position in which they are at least partially disengaged from one another.

[0013] According to the invention, one of the stator and the rotor comprises two active parts for producing eddy currents which are axially movable relative to each other to be brought closer to each other when the stator and the rotor are in the maximum braking position and separated from each other when the stator and the rotor are in the free rotation position.

[0014] By active part in the production of eddy currents is meant either a magnetic flux emitting part (carrying the magnets) or a magnetic flux receiving part (in which the eddy currents are intended to circulate). Thus, the two rotor or stator parts are moved relative to each other in two opposite directions to bring the rotor and stator into the maximum braking position or into the free rotation position. The travel between these two positions can therefore be divided by two compared to stator and rotor in a single part: the displacement from one position to another is therefore faster and requires less bulky actuators.

[0015] According to optional characteristics, used in whole or in part, individually or in combination: - said parts belong to the stator, each of said parts preferably having a length substantially equal to half a length of the rotor; - said parts are dimensioned to be completely clear of the other of the stator and the rotor when the stator and the rotor are in the free rotation position; - said parts each carry a plurality of magnets.

[0016] The invention also relates to a braked wheel equipped with such a device, an aircraft landing gear equipped with such a wheel and an aircraft equipped with such a landing gear.

[0017] 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

[0018] Reference will be made to the accompanying drawings, among which:

[0019] [Fig-1] [Fig.l] is a partial schematic view of an aircraft equipped with a landing gear according to the invention;

[0020] [Fig.2] [Fig.2] is a perspective view of an aircraft wheel, without the braking device;

[0021] [Fig.3] [Fig.3] is a perspective view of an aircraft wheel according to the invention, with the braking device;

[0022] [Fig.4] [Fig.4] is a half axial sectional view of this wheel, with the braking device in a braking state;

[0023] [Fig.5] [Fig.5] is a half-view in axial section of this wheel, with the braking device in a state of free rotation of the wheel;

[0024] [Fig.6] [Fig.6] is a half-view in axial section of this wheel according to an alternative embodiment of the invention, with the braking device in a braking state;

[0025] [Fig.7] [Fig.7] is a half-view in axial section of the wheel according to this variant, with the braking device in a state of free rotation of the wheel. DETAILED DESCRIPTION OF THE INVENTION

[0026] With reference to [Fig.l], 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.

[0027] Also with reference to [Fig.2], each wheel 103 comprises in a known manner in a hub 104 mounted to pivot on the shaft 102 and a rim 105 connected to the hub 104 by a web 106 defining with the hub 104 an annular space 107 open opposite the web 106. The rim 105 comprises two external rims including a rim 108 located on the side of the entrance to the annular space 107. Bars 109.1, integral with the rim 105, extend projecting from the rim 105 into the annular space 107 and bars 109.2, integral with the rim 108 of the rim 105, extend projecting towards the outside of the rim 108 of the rim 105. Bearings 110 (visible in [Fig.4]) ensure the rotational guidance of the hub 104 on the shaft 102.

[0028] As visible in [Fig.3], the wheels 103 are equipped with a magnetic braking device, generally designated 1, housed in an annular space 107 defined between the hub 104 and the rim 105.

[0029] Also referring to Figures 4 and 5, the magnetic braking device 1 comprises a fixed rotating element, namely a stator 2, and a mobile rotating element, namely a rotor 3. The stator 2 has the shape of an internal drum and the rotor 3 has the shape of an external drum in which the stator 2 can be engaged, the stator 2 and the rotor 3 being coaxial with the wheel 103 and therefore having collinear central axes.

[0030] More precisely here, the stator 2 comprises a first ring 2.1 and a second ring 2.2.

[0031] The ring 2.1 comprises a tubular part which has one end provided with a radial collar intended to extend opposite the rim 108. The tubular part is provided externally with magnets 10.1 defining an external cylindrical surface of the ring 2.1. The tubular part of the ring 2.1 has one end provided with an externally projecting radial collar, which is intended to extend opposite the rim 108 and on which the permanent magnets 10.1 also extend, which define a front radial surface of the ring 2.1. The magnets 10.1 are here based on rare earths and are preferably fixed on a magnetic steel support, or on a non-magnetic support.

[0032] The ring 2.2 comprises a tubular part which is devoid of a collar but carries, like the tubular part of the ring 2.1, permanent magnets 10.2, defining an external cylindrical surface of the ring 2.2. The magnets 10.2 are here based on rare earths and are preferably fixed on a magnetic steel support, or on a non-magnetic support.

[0033] The rotor 3 comprises a tubular part received in the rim 105 and provided externally with external axial grooves engaged on the bars 109.1. The tubular part of the rotor 3 has a cylindrical internal surface and has one end provided with an externally projecting radial collar, which is intended to extend opposite the edge 108. The collar of the rotor 3 has a radial surface facing the radial surface of the ring 2.1 of the stator 2 and comprises, on the opposite side, grooves engaged on the bars 109.2. It is understood that the bars 109.1, 109.2 connect in rotation the rotor 3 and the rim 105. The rotor 3 is made of copper or any other electrically conductive material. A screen 4 is installed between the rotor 3 on the one hand and the rim 105 and the rim 108 on the other hand. The screen 4 is here made of iron and has a magnetic screen function to prevent the magnetic flux from heating the wheel in the case where the wheel is not intended to form a heat sink but also a heat screen function to protect the rim 105 and the rim 108 from the heat generated by the operation of the magnetic braking device 1.

[0034] As previously indicated, the rings 2.1 and 2.2 of the stator are intended to be engaged in the rotor 3. For this purpose, the external cylindrical surface of the ring 2.1 has a diameter slightly smaller than the diameter of the internal cylindrical surface of the rotor 3 and the external cylindrical surface of the ring 2.2 has a diameter slightly smaller than the diameter of the internal cylindrical surface of the rotor 3. A radial air gap is therefore defined between the external cylindrical surfaces of the stator 2 and the internal cylindrical surface of the rotor 3 and an axial air gap is defined between the radial surfaces of the stator 2 and the rotor 3.

[0035] The magnets 10.1 produce axial magnetic fluxes in the axial air gap and radial magnetic fluxes in the radial air gap and the magnets 10.2 produce radial magnetic fluxes in the radial air gap. These magnetic fluxes are capable of generating eddy currents in the rotor 3 when the rotor 3 pivots opposite the stator 2. These eddy currents are all the more powerful as the air gaps are small and the variation in the air gap is used to control the activation of the magnetic braking device 1.

[0036] More precisely, the ring 2.1 and the ring 2.2 are mounted to slide axially on a crown 5 fixed by bolts 6 to a collar 102' extending in external projection from the shaft 102. The crown 5 is provided with axial ribs 7 received in internal grooves of the rings 2.1, 2.2 to ensure the translational guidance of the rings 2.1, 2.2 on the crown 5.

[0037] The rotor 3, the stator 2 and the ring 5 are therefore coaxial and are positioned successively, in this order, in a radial direction of the wheel 103. The stator 2 is connected in rotation to the shaft 102 while the rotor 3 is connected in rotation to the wheel 103, here to the rim 105 of the wheel 103. Thus, the 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 internal cylindrical surface of the rotor 3 remains opposite the external cylindrical surfaces of the stator 2 and parallel to them; and the radial surfaces of the rotor 3 and of the stator 2 remain opposite one another and parallel to each other.

[0038] The magnetic braking device 1 comprises an actuating device 8 for moving the rings 2.1, 2.2 between: - a braking position (shown in [Fig.4]) in which the parts you the radial surfaces of the rings 2.1, 2.2 are fully engaged in the rotor 3 and the radial surfaces of the stator 2 and the rotor 3 are as close as possible to each other; and - a position of free rotation of the wheel 103 (shown in [Fig.5]) in which the tubular parts of the rings 2.1, 2.2 are completely extracted from the rotor 3 and the radial surfaces of the stator 2 and the rotor 3 are as far apart as possible from each other.

[0039] The actuating device 8 comprises one or more actuators mounted on the crown 5. Each actuator may comprise: - a screw, driven by an electric motor or a common gear train, having a first section and a second section having reversed pitches such that the ring 2.1 mounted on the first section and the ring 2.2 mounted on the second section move in opposite directions relative to each other when the screw is driven in a first direction of rotation and vice versa when the screw is driven in a second direction of rotation and vice versa; and / or - two linear motors or actuators each associated with one of the rings and controlled to bring the rings closer to each other or move them away from each other; and / or - a structure of connecting rods articulated together to form deformable parallelograms...

[0040] These actuators are known in themselves and will not be described further here.

[0041] It is understood that the actuating device 8 is controlled to axially bring the rings 2.1, 2.2 together to bring the stator 2 and the rotor 3 into the maximum braking position and to separate the rings 2.1, 2.2 from each other to bring the stator 2 and the rotor 3 into the free rotation position.

[0042] Indeed, as each of the tubular parts of the rings 2.1, 2.2 has a length at least equal, and here substantially equal, to half a length of the tubular part of the rotor 3: - the entire internal surface of the rotor 3 is subjected to the magnetic fields produced by the magnets 10.1, 10.2 when the rings 2.1, 2.2 are closest to each other; - the internal surface of the rotor 3 is no longer subjected to the magnetic fields produced by the magnets 10.1, 10.2 when the rings 2.1, 2.2 are moved away from each other and have been extracted from the rotor 3.

[0043] It will be noted that this arrangement not only makes it possible to limit the travel required to move the stator between the maximum braking and free rotation positions but also to bring the wheel 103 and the leg of the landing gear 101 closer together.

[0044] In the embodiment of Figures 6 and 7, the ring 2.1 of the stator 2 and the rotor 3 are devoid of collars so that the magnets 10.1 are arranged to generate only a radial flux.

[0045] It will be noted that the plurality of permanent magnets can advantageously be arranged according to a Halbach pattern with first magnets having a first magnetization vector locally perpendicular to the external cylindrical surface of the stator 2 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 said second magnet is located. The second magnets arranged on each side of the same first magnet have their magnetization vector oriented in opposite directions. 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.The first magnets may be spaced two by two by a first distance (equal to the width of the second magnets) less than a second distance (equal to the width of the first magnets) separating the second magnets two by two. The best results are obtained when the width of the second magnets is approximately 70% of that of the first magnets. The lengths of the magnets may be identical to each other, or not. Preferably, the second magnets occupy a smaller surface area on the external cylindrical surface of the stator 2 than that of the first magnets. This arrangement of the magnets makes it possible to optimize and concentrate the magnetic flux produced by the first magnets by reducing the return path of the magnetic flux which passes through the second magnets and not through their support, the mass of which may be reduced since it does not need to perform a magnetic flux conduction function.

[0046] It will be noted that below a certain rotational speed of the rotor 3, the braking torque is negligible regardless of the air gap. It will then be necessary to consider an additional brake also serving as a parking brake.

[0047] 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.

[0048] In particular, the device may have a structure different from that described.

[0049] The shape, arrangement and dimensions of the magnets may be different from those described. For example, magnets all have the same dimensions.

[0050] The number of rotors and / or the number of stators may be different from those mentioned.

[0051] 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.

[0052] The rotor may be connected to the shaft 102 or to the landing gear leg 101.

[0053] The magnetic braking device may comprise one or more electromagnets with or instead of permanent magnets.

[0054] The rotor may carry the magnets, the stator(s) comprising an electrically conductive material such as copper.

[0055] The rotor or stator can be in two parts, regardless of whether it carries the magnets or not.

[0056] The invention can be used on any type of vehicle, for example aerial, land or amphibious vehicles, or any industrial or transport mobile equipment requiring braking.

Claims

Claims

1. Eddy current magnetic braking device (1), comprising a stator (2) and a rotor (3) one of which carries a plurality of permanent magnets (10.1, 10.2) for emitting towards the other a first radial magnetic flux capable of generating eddy currents when the stator and the rotor are engaged in each other in a maximum braking position, the stator (2) and the rotor (3) being movable relative to each other between the maximum braking position and a free rotation position in which they are at least partially disengaged from each other, characterized in that one of the stator and the rotor comprises two parts (2.1, 2.2) active for the production of eddy currents which are axially movable relative to each other to be brought closer to each other when the stator (2) and the rotor (3) are in the maximum braking position and separated from each other when the stator (2) and the rotor (3) are in the free rotation position.

2. Device according to claim 1, wherein said parts (2.1, 2.2) belong to the stator.

3. Device according to claim 2, wherein each of said parts (2.1, 2.2) has a length substantially equal to half a length of the rotor.

4. A device according to any preceding claim, wherein said portions (2.1, 2.2) are dimensioned to be completely clear of each other of the stator and rotor when the stator and rotor are in a freely rotating position.

5. Device according to any one of the preceding claims, wherein said parts (2.1, 2.2) each carry a plurality of the magnets (10.1, 10.2).

6. Braked vehicle wheel (103) comprising a braking device (1) according to any one of the preceding claims, comprising a rim (105), a disc (106) or a hub (104) to which the rotor (3) of the braking device is rotationally connected.

7. Landing gear (101) comprising a leg having one end carrying a shaft (102) on which is mounted the hub (104) of a wheel (103) according to claim 6, the stator (2) of the braking device (1) being rotationally linked to the leg.

8. An aircraft (100) comprising a landing gear (101) according to claim 7.

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