FR3147553A1 - Eddy current magnetic braking device, vehicle braked wheel, aircraft landing gear and aircraft equipped with such a wheel - Google Patents

Abstract

Eddy current magnetic braking device (1) for a vehicle wheel, comprising at least one stator (2) and one rotor (3), and magnets (4) integral with one of these to produce between them an axial magnetic flux capable of generating eddy currents in the other of these when the wheel rotates. One of the rotor (3) and the stator (2) is a disk and the other of the rotor (3) and the stator (2) is a crown divided into at least two crown sectors (2A, 2B, 2C, 2D) movable radially between a first position in which each crown sector (2A, 2B, 2C, 2D) has at least one face (2.1, 2.2) facing a face (3.1, 3.2) of the disk to establish the axial magnetic flux and a second position in which said at least one face (2.1, 2.2) of the crown sector (2A, 2B, 2C, 2D) is radially offset relative to the face (3.1, 3.2) of the disk to interrupt the axial magnetic flux. Aircraft wheel, landing gear and aircraft comprising such a device. FIGURE OF THE ABSTRACT: Fig. 3

Description

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

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

BACKGROUND OF THE INVENTION

An aircraft wheel typically consists of a rim surrounded by a tire and connected by a web to a hub mounted to rotate on a wheel support shaft (axle or spindle).

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

Eddy current magnetic braking devices are also known, used for braking vehicle wheels and more particularly aircraft wheels. Document FR-A-3122405 describes such a device comprising a rotor rotatably connected to the wheel, two stators which surround the rotor and which are rotatably connected to the wheel support shaft and free in translation relative to said shaft, magnets for producing an axial magnetic flux between the stators and the rotor, and linear actuators for axially moving the stators between a maximum braking position in which the stators are close to the rotor and a free rotation position of the wheel in which the stators are far from the rotor.

To eliminate any resistance to the rotation of the wheel in such an axial flux magnetic braking device, it is necessary for the distance between the stators in the free rotation position and the rotor to be large, which increases the axial size of the device while the latter is often already constrained, in particular on a retractable aircraft landing gear which generally has holds with a determined volume to accommodate the landing gear as closely as possible. As a result, if the maximum spacing between the stators and the rotor is not sufficient, for example limited by the size constraints, there remains a residual braking torque even though the brake is supposed to be deactivated.

Furthermore, 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 an aircraft, even though mass and size are severe constraints for this use.

SUBJECT OF THE INVENTION

The invention aims in particular to propose a braking device which at least partially overcomes the aforementioned drawbacks.

For this purpose, the invention provides an eddy current magnetic braking device for a vehicle wheel, comprising at least one stator and one rotor, and magnets secured to one of them to produce between them an axial magnetic flux capable of generating eddy currents in the other of them when the wheel rotates. One of the rotor and the stator is a disk and the other of the rotor and the stator is a crown divided into at least two radially movable crown sectors between a first position in which each crown sector has at least one face facing a face of the disk to establish the axial magnetic flux and a second position in which said at least one face of the crown sector is radially offset relative to the face of the disk to interrupt the axial magnetic flux, the device comprising at least one actuator connected to the crown sectors to move the crown sectors between their two positions.

Thus, the crown sectors move between their two positions in a radial direction without increasing the axial size of the device. The two positions of the crown sectors can therefore be sufficiently spaced apart so that, in their second position, the magnetic flux is interrupted between stator and rotor.

• chaque secteur de couronne a une section en U pour pouvoir chevaucher une portion du disque en ayant des branches s’étendant chacune d’un côté du disque de sorte que chaque secteur de couronne comporte au moins une première face en regard d’une première face du disque et une deuxième face en regard d’une deuxième face du disque opposée à la première face du disque ;
• les secteurs de couronne sont au nombre de quatre s’étendant chacun sur 90° ;
• chaque secteur de couronne est relié à un actionneur, les actionneurs étant disposés en opposition par paire ;
• les aimants sont solidaires de la couronne, chaque secteur de couronne portant plusieurs des aimants disposés en alternance sur un arc de cercle coaxial à la couronne ;
• la couronne est le stator et le disque est le rotor.

The device may include all or some of the following additional features, separately or in combination:

• each crown sector has a U-shaped section to be able to overlap a portion of the disk by having branches each extending on one side of the disk such that each crown sector comprises at least a first face facing a first face of the disk and a second face facing a second face of the disk opposite the first face of the disk;
• the crown sectors are four in number, each extending over 90°;
• each crown sector is connected to an actuator, the actuators being arranged in opposition in pairs;
• the magnets are integral with the crown, each crown sector carrying several of the magnets arranged alternately on an arc of a circle coaxial with the crown;
• the crown is the stator and the disc is the rotor.

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

Other characteristics and advantages of the invention will emerge from reading the following description of particular and non-limiting embodiments of the invention.

Reference will be made to the attached drawings, including:

there is a partial schematic front view of an aircraft equipped with landing gear according to the invention;

there is a partial schematic view of a wheel according to the invention, in axial half-section, the crown sectors being in their second position or position of free rotation of the wheel;

there is a schematic perspective view of this wheel, the crown sectors being in their second position;

there is a schematic perspective view of this wheel, with the crown sectors in their first or maximum braking position.

DETAILED DESCRIPTION OF THE INVENTION

With reference to figures 1 to 4, 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 shaft 102 having a central axis defining an axis X of rotation of the wheel 103 which it carries. 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. The rim 105 and the hub 104 define between them an annular space 107 having one end closed by the web 106 and one end open towards the outside of the wheel 103 forming an entrance to the annular space 107. The rim 105 is surrounded by a tire, not shown, received between two lips 108 of the rim 105.

According to the invention, the wheels 103 are equipped with a magnetic braking device generally designated 1, which extends in front of the entrance to the annular space 107, outside the latter.

The magnetic braking device 1 comprises a fixed element, or stator 2, and a mobile element, or rotor 3.

More precisely here, the stator 2 has a crown shape coaxial with the wheel 103 and the shaft 102.

More precisely, the stator 2 is divided into four crown sectors 2A, 2B, 2C, 2D, identical to each other, extending at an angle of 90°. Each crown sector 2A, 2B, 2C, 2D has a U-shaped cross-section (along a plane containing the X axis) with two branches facing each other. Each branch preferably comprises a non-magnetic support provided with a plurality of permanent magnets 4, having free faces (opposite the branch which carries them) and generating magnetic fields to produce a magnetic flux in the direction of the branch located opposite, that is to say an axial magnetic flux parallel to the axis X. The two branches of each crown sector 2A, 2B, 2C, 2D, thus provided with magnets 4, delimit between them a groove whose sides are formed by faces 2.1, 2.2 formed by the free faces of the magnets 4.

The crown sectors 2A, 2B, 2C, 2D forming the stator 2 are linked in rotation to the shaft 102 or to the leg of the landing gear 101, here by means of a plate 5. The plate 5 comprises a tube 5.1 engaged on an external collar 102' of the shaft 102, an internal collar 5.2 which is fixed by screws to the collar 102', and an external collar 5.3 carrying actuators 6 here hydraulic. The actuators 6 are eight in number arranged in pairs at 90° to each other and each crown sector 2A, 2B, 2C, 2D is connected to the two actuators 6 of one of the pairs. The actuators 6 of each pair are arranged in opposition to the actuators 6 of the pair of actuators which is at 180° relative to them. The actuators 6 may have a body fixed to the external collar 5.3 of the plate 5 but here have a body 6.1 in a single piece with the external collar 5.3 of the plate 5. The body 6.1 of each actuator 6 slidably receives a piston 6.2 which is movable in translation in a radial direction and which has a free end section on which is fixed one of the branches of one of the crown sectors 2A, 2B, 2C, 2D so that each crown sector 2A, 2B, 2C, 2D is carried and guided by the two actuators 6 of the same pair of actuators.

The rotor 3 is made of copper or any other electrically conductive material and has the shape of an annular disk coaxial with the wheel 103 and the shaft 102. The rotor 3 has an internal periphery connected to the rim 105 by a sleeve 7 to be coaxial with the shaft 102 and is surrounded by the crown sectors 2A, 2B, 2C, 2D. The rotor 3 has two faces 3.1, 3.2, main and opposite to each other, between which extends parallel a median plane merged with a median plane of the groove extending parallel and halfway between the faces 2.1, 2.2. The faces 3.1, 3.2 are parallel to the faces 2.1, 2.2. The rotor 3 is therefore linked in rotation to the wheel 103, here to the rim 105 of the wheel 103 by means of the sleeve 7, and rotates on itself around its central axis relative to the crown sectors 2A, 2B, 2C, 2D which surround it: during this movement of the rotor 3 in a circumferential direction relative to the crown sectors 2A, 2B, 2C, 2D, the main faces 3.1, 3.2 remain parallel to the main faces 2.1, 2.2.

• une première position, ou position de freinage maximal de la roue 103, dans laquelle les secteurs de couronne 2A, 2B, 2C, 2D du stator 2 sont rapprochés du rotor 3, les secteurs de couronne 2A, 2B, 2C, 2D chevauchant un pourtour externe du rotor 3, de sorte que les faces 2.1, 2.2 du stator 2 s’étendent en regard des faces 3.1, 3.2 du rotor 3 en étant séparées de celles-ci par un premier entrefer prédéterminé et ;
• une deuxième position, ou position de rotation libre de la roue 103, dans laquelle les secteurs de couronne 2A, 2B, 2C, 2D du stator 2 sont écartés du rotor 3, les secteurs de couronne 2A, 2B, 2C, 2D étant dégagés du pourtour externe du rotor 3, de sorte que les faces 2.1, 2.2 du stator 2 sont décalées radialement vers l’extérieur par rapport aux faces 3.1, 3.2 du rotor 3 et sont séparées des faces 3.1, 3.2 par un deuxième entrefer prédéterminé supérieur au premier entrefer prédéterminé.

The actuators 6 move the crown sectors 2A, 2B, 2C, 2D in a radial direction of the wheel 103 between:

• a first position, or maximum braking position of the wheel 103, in which the crown sectors 2A, 2B, 2C, 2D of the stator 2 are brought closer to the rotor 3, the crown sectors 2A, 2B, 2C, 2D overlapping an external periphery of the rotor 3, so that the faces 2.1, 2.2 of the stator 2 extend opposite the faces 3.1, 3.2 of the rotor 3 while being separated from the latter by a first predetermined air gap and;
• a second position, or free rotation position of the wheel 103, in which the crown sectors 2A, 2B, 2C, 2D of the stator 2 are spaced from the rotor 3, the crown sectors 2A, 2B, 2C, 2D being clear of the external periphery of the rotor 3, so that the faces 2.1, 2.2 of the stator 2 are offset radially outwards relative to the faces 3.1, 3.2 of the rotor 3 and are separated from the faces 3.1, 3.2 by a second predetermined air gap greater than the first predetermined air gap.

When the crown sectors 2A, 2B, 2C, 2D are in the maximum braking position, the rotor 3 has portions arranged between the branches of the crown sectors 2A, 2B, 2C, 2D and has its opposite faces 3.1, 3.2 facing the faces 2.1, 2.2 of the stator 2 respectively.

When the crown sectors 2A, 2B, 2C, 2D are in the maximum braking position, the magnetic field of the magnets 4 produces a magnetic flux sufficient to generate eddy currents in the rotor 3 when the rotor 3 pivots opposite the magnets 4.

The rotor 3 has a thickness such that a skin effect (otherwise called a skin effect or Kelvin effect) is generated from each face 3.1, 3.2 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 crown sectors 2A, 2B, 2C, 2D. The eddy currents generated from the two faces 3.1, 3.2 will then circulate in the central part of the rotor 3, which will increase the braking torque. This gives in the central part a “superposition of the skin effects” produced from each face 3.1, 3.2, the thickness of the rotor 3 being sufficiently small to obtain this superposition while satisfying the thermal and mechanical constraints. In one example, this superposition gives approximately 60% more performance.

It will be noted that the branch of each angular sector arranged on the side of face 3.2 provides a heat shield function preventing the heat generated in the rotor 3 by the eddy currents from being transmitted to the rim 105 and the tire it carries.

The actuators 6 are controlled in a manner known per se to synchronously move the crown sectors 2A, 2B, 2C, 2D between their two positions.

It is understood that to cause braking, the actuators 6 are controlled to bring the stators 2 into the first position and that, to interrupt braking, the actuators 6 are controlled to bring the crown sectors 2A, 2B, 2C, 2D of the stator 2 into the second position, a position in which the magnets 4 do not allow sufficient eddy currents to be generated in the rotor 3 to cause braking of the rotor 3.

It should be noted that below a certain rotation speed of the rotor 3, the braking torque is negligible regardless of the position of the crown sectors 2A, 2B, 2C, 2D of the stator 2. It may then be necessary to consider an additional brake.

The actuator control circuit 6 conventionally comprises an electronic brake control unit which receives as input a control signal from an instrument operated by the pilot of the aircraft 100 and transmits control signals to an actuator control unit which produces, from the control signal, a power signal transmitted to the actuators 6 to modify the value of the air gap between the ring sectors 2A, 2B, 2C, 2D of the stator 2 and the rotor 3 according to the braking force required by the pilot. The modification of the air gap by the actuators 6 will increase or decrease the braking torque and therefore the speed of the aircraft 100. The modification of the air gap by the actuators 6 affects the magnetic flux transmitted to the rotor 3 by the magnets 4. This arrangement is conventional and will not be described further here.

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.

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

The magnets can be carried by the rotor instead of the stator, with two rotors surrounding a stator.

The shape, arrangement and dimensions of the magnets may differ from those described or shown. For example, the magnets may have different dimensions and/or be arranged in a HALBACH pattern.

Magnets may include electromagnets.

The number of rotors and/or the number of stators may be different from those mentioned. For example, each crown sector of the stator may comprise three branches (or more) forming between them two grooves (or more) each accommodating a portion of a rotor. Conversely, each crown sector of the stator may comprise only one branch. A heat shield will then be provided between the rotor and the rim to prevent the heat generated in the rotor by the eddy currents from being transmitted to the rim.

The device may comprise means for guiding the crown sectors in radial translation. For example, the plate is provided with radial guides along which the crown sectors are mounted to slide.

Each crown sector may extend less than 90° or more than 90°. The number of crown sectors may be less than four, for example two or three, or more than four, for example six.

The crown sectors can be engaged on an external periphery or an internal periphery of the disc.

The invention also applies to a device in which the crown forms the rotor.

The magnetic braking device according to the invention can be associated with a conventional friction braking device, for example to provide braking at low speed or when parking. Such a friction braking device comprises friction members, for example a stack of carbon disks housed in the annular space 107, 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 disks. The electromechanical actuator is thus intended to produce a controlled braking force on the stack of disks. A method of controlling the braking devices is for example known from document FR-A-2953196.

• des actionneurs hydrauliques ou électromécaniques,
• des actionneurs linéaires,
• des actionneurs rotatifs ayant par exemple un pignon de sortie engrenant avec une crémaillère liée au secteur de couronne,
• des actionneurs à simple effet (un élément élastique assurant le rappel en position de rotation libre) ou à double effet,
• ou autres.

Actuators may include:

• hydraulic or electromechanical actuators,
• linear actuators,
• rotary actuators having for example an output pinion meshing with a rack linked to the crown sector,
• single-acting actuators (an elastic element ensuring return to the free rotation position) or double-acting actuators,
• or others.

The actuator body can be in one piece with the actuator carrier plate. The actuator carrier plate can have any suitable shape.

It is possible to use, for the mechanical actuation of the magnetic braking device, an actuator acting on several crown sectors, rather than an actuator for each crown sector. A single actuator can thus act on two crown sectors diametrically opposed to each other to move them in opposite directions. The actuators can be single-acting and incorporate a spring to automatically return them to the disengaged position in the absence of power.

The invention can be used on any type of vehicle in contact with the ground by at least one wheel and requiring braking, for example aerial, land or amphibious vehicles, transport or industrial equipment.

Claims (10)

Eddy current magnetic braking device (1) for a vehicle wheel, comprising at least one stator (2) and one rotor (3), and magnets (4) integral with one of these to produce between them an axial magnetic flux capable of generating eddy currents in the other of these when the wheel rotates, characterized in that one of the rotor (3) and the stator (2) is a disk and the other of the rotor (3) and the stator (2) is a crown divided into at least two crown sectors (2A, 2B, 2C, 2D) radially movable between a first position in which each crown sector (2A, 2B, 2C, 2D) has at least one face (2.1, 2.2) facing a face (3.1, 3.2) of the disk to establish the axial magnetic flux and a second position in which said at least one face (2.1, 2.2) of the crown sector (2A, 2B, 2C, 2D) is radially offset relative to the face (3.1, 3.2) of the disk to interrupt the axial magnetic flux, the device comprising at least one actuator (6) connected to the crown sectors (2A, 2B, 2C, 2D) to move the crown sectors (2A, 2B, 2C, 2D) between their two positions. Device according to claim 1, in which each crown sector (2A, 2B, 2C, 2D) has a U-shaped section to be able to overlap a portion of the disk by having branches each extending on one side of the disk so that each crown sector (2A, 2B, 2C, 2D) comprises at least a first face (2.1) facing a first face (3.1) of the disk and a second face (2.2) facing a second face (3.2) of the disk opposite the first face (3.1) of the disk. Device according to claim 1 or 2, in which the crown sectors (2A, 2B, 2C, 2D) are four in number, each extending over 90°. Device according to claim 3, in which each crown sector (2A, 2B, 2C, 2D) is connected to an actuator (6), the actuators (6) being arranged in opposition in pairs. Device according to any one of the preceding claims, in which the magnets (4) are integral with the crown, each crown sector (2A, 2B, 2C, 2D) carrying several of the magnets (4) arranged alternately on an arc of a circle coaxial with the crown. Device according to any one of the preceding claims, in which the crown is the stator (2) and the disc is the rotor (3). Braked vehicle wheel (103), comprising a rim (105) and a hub (104) connected by a web (106) defining an annular space (107), and a braking device (1) according to any one of the preceding claims placed in front of an entrance to the annular space (107), the crown being integral with a plate (5) arranged to be connected in rotation to a support shaft (102) of the wheel. Wheel according to claim 7, in which the actuator (6) has a body (6.1) in one piece with an external collar (5.3) of the plate (5). Landing gear (101) comprising a leg having one end carrying the shaft (102) on which is mounted the hub (104) of a wheel (103) according to claim 7 or claim 8, the plate (5) being fixed to an external collar (102') of the shaft (102). Aircraft (100) comprising at least one landing gear (101) according to claim 9.