Aircraft landing gear comprising a wheel with integrated magnetic braking device

Abstract

The invention relates to a landing gear for an aircraft comprising a leg having an end carrying a shaft on which a wheel (103) is mounted. The wheel comprises a hub (104.1) and a rim (105.1) that is coaxial with the hub and connected to the hub via a disc portion (106.1). The wheel comprises an eddy-current magnetic braking device (1) comprising a rotor (3) that is rotatably connected to the wheel and a stator (2) that is rotatably connected to the leg, that is rotatable with respect to the rim (105.1) and to the rotor (3), and that carries a plurality of magnets (11, 12, 13, 14) capable of emitting a magnetic flux in the rotor. The rotor is made of an electrically conductive material so as to be able to give rise to eddy currents and the rotor is formed of one piece with the rim (105.1).

Description

[0001]AIRCRAFT LANDING GEAR WITH WHEEL AND MAGNETIC BRAKING DEVICE AND AIRCRAFT EQUIPPED WITH SUCH A LANDING GEAR The present invention relates to the field of braking vehicle wheels such as aircraft wheels. The invention applies more particularly to magnetic braking devices, i.e. devices in which a magnetic field is used to produce a braking force. BACKGROUND OF THE INVENTION An aircraft wheel generally comprises a rim connected by a disc to a hub mounted to rotate on a wheel support shaft (axle or spindle). 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.magnetic brakes 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. 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 magnets and which is attached to the wheel opposite an electromagnetic stator fixed relative to the landing leg carrying the wheel. 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 the massand the size are severe constraints for this use. OBJECT OF THE INVENTION The invention aims in particular to propose a landing gear provided with a wheel equipped with an eddy current magnetic braking device at least partially overcoming the aforementioned drawbacks. SUMMARY OF THE INVENTION To this end, the invention provides an aircraft landing gear having a wheel comprising at least one hub part and a rim part coaxial with the hub part and connected to the hub part by a sail part, the wheel comprising an eddy current magnetic braking device comprising a rotor connected in rotation to the wheel and a stator which is rotatable relative to the rim part and to the rotor and which carries a plurality of magnets capable of emitting a magnetic flux generating in the rotor, made of electrically conductive material, eddy currents when the stator and the rotor are facing each other.and in relative motion. The rotor is made of a single piece with the rim portion. Thus, at least part of the wheel and the rotor are manufactured in a single piece, for example by casting or additive manufacturing, which improves the integration of the rotor into the wheel and eliminates the need to use means for fixing the rotor to the rim. It is therefore possible to obtain a simpler, more compact and lighter structure than that of conventional braked wheels. According to optional features, used individually or in whole or in part in combination: - the rotor and the stator have radial surfaces facing each other and the magnets are positioned on the stator to emit a magnetic field between these surfaces parallel to a central axis of the wheel; - the rotor comprises a crown extending laterally relative to a lip of the rim portion and connected to said rim portion by a connecting portion, the connecting portion having a cross-sectiontransverse less than a cross-section of the rotor crown; - the rotor and the stator have axial surfaces facing each other and the magnets are positioned on the stator to emit a magnetic field between these surfaces perpendicular to a central axis of the wheel; - the rotor comprises a tube which is coaxial with the hub portion and extends between the rim portion and the hub portion, the tube has an internal surface forming the axial surface of the rotor; - the rotor and the stator have first radial surfaces facing each other and the magnets comprise first magnets positioned on the stator to emit a magnetic field between the first surfaces parallel to a central axis of the wheel and wherein the rotor and the stator also have second axial surfaces facing each other and the magnets comprise second magnets positioned on the stator to emit a magnetic field between thesecond surfaces perpendicular to a central axis of the wheel; - the rotor comprises a tubular portion extending projecting from the rim portion; - the wheel comprises solid heat storage portions in the vicinity of the rotor, said solid portions being in one piece with the rim portion; - the magnets are arranged in a Halbach pattern. The invention also relates to an aircraft equipped with such a landing gear. 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 Reference will be made to the appended drawings, among which: [Fig. 1] Figure 1 is a partial schematic view of an aircraft equipped with landing gears according to the invention; [Fig. 2] Figure 2 is a schematic view in axial half-section of a wheel according to a first embodiment of the invention; [Fig. 3] Figure 3 is a viewpartial schematic view in perspective and in axial half-section of this wheel; [Fig. 4] Figure 4 is a view similar to that of Figure 2 of a wheel according to a second embodiment of the invention; [Fig. 5] Figure 5 is a view similar to that of Figure 2 of a wheel according to a third embodiment of the invention; [Fig. 6] Figure 6 is a schematic view showing a possible arrangement of the magnets in a wheel according to the invention. DETAILED DESCRIPTION OF THE INVENTION With reference to Figures 1 to 6, the invention is described in application to an aircraft 100 comprising landing gears 101. Each landing gear 101 comprises a leg having a first end articulated to a structure of the aircraft and, opposite, a second, free end, provided with two coaxial shafts 102 on each of which is mounted to pivot a wheel 103. The landing gears 101 are here of the retractable type but the invention is applicable to fixed landing gears, or even to aanother type of vehicle such as a land vehicle. Each wheel 103 here comprises, in a manner known per se, two half-wheels 103.1, 103.2 which are each made in a single piece and which are bolted to each other. Each half-wheel 103.1, 103.2 comprises a hub part 104.1, 104.2 and a rim part 105.1, 105.2 connected to the hub part 104.1, 104.2 by a web part 106.1, 106.2. Each rim part 105.1, 105.2 has an annular shape having a first annular edge integral with the web part 106.1, 106.2 and a second opposite annular edge provided with a rim or lip 107.1, 107.2. We speak of a half-wheel but also commonly of a half-rim, half-sail, half-hub even though these parts do not represent half of a wheel, rim, sail, hub. Each half-wheel 103.1, 103.2 is here made of aluminum. When the half-wheels 103.1, 103.2 are bolted to each other: - the hub parts 104.1, 104.2 form a hub which can be mountedto pivot on the shaft 102; - the rim parts 105.1, 105.2 form a rim capable of receiving a tire between the lips 107.1, 107.2; - the web parts 106.1, 106.2 are pressed against each other by the bolts and form a web transmitting the forces between the hub and the rim. The rim part 105.1 extends opposite the hub part 104.1: together they define an annular space having one end at least partially closed by the web part 106.1 and, opposite, an open end on the side of the lip 107.1. The wheels 103 are equipped with a magnetic braking device generally designated 1. The magnetic braking device 1 comprises a fixed element, or stator 2, and a movable element, or rotor 3. The stator 2 and the rotor 3 are coaxial with the rim portion 105.1; the stator 2, the rotor 3 and the hub portion 104.1 therefore have collinear central axes. The stator 2 comprises a plurality of magnets capable of generatingeddy currents in the rotor 3 when the stator 2 and the rotor 3 are separated by a small air gap and the rotor 3 pivots relative to the stator 2. According to the invention, the rotor 3 is in one piece with the rim part 105.1 and therefore in one piece with the half-wheel 103.1. The rotor 3 and the half-wheel 103.1 are therefore made of the same material, namely aluminum. According to the first embodiment shown in Figures 2 and 3, the rotor 3 has the shape of a crown extending in front of the lip 107.1 coaxially therewith. The crown forming the rotor 3 has: - a radial face defining a first main surface 3.1 of the rotor 3, flat, which extends transversely to the central axis of the wheel 103 and which is turned away from the lip 107.1; - an internal periphery defining a second main surface 3.2 of the rotor 3, cylindrical, which extends axially and defines an internal periphery of the radial annular part of the crown; The rotor 3is connected to the rim portion 105.1 by a connecting ring 4 which extends in the extension of the second main surface 3.2 and of the rim portion 105.1 beyond the lip 107.1. The connecting ring 4 is pierced with radial holes 5 providing several functions and in particular limiting the mass of the wheel 103. The stator 2 here has the shape of a crown which extends opposite the rotor 3 coaxially thereto and which has an internal axial rim. The stator 2 has an L-shaped cross-section and comprises: - a radial face provided with a first series of magnets defining a first main surface 2.1 of the stator 2, flat, which extends transversely to the central axis of the wheel 103 and which is turned towards the rotor 3; - an internal periphery provided with a second series of magnets defining a second main surface 2.2 of the stator 2, cylindrical, which extends axially so as to be able to be engaged in the second main surface 3.2 of the rotor 3. The stator 2 islinked in rotation to the shaft 102, here by means of a fixing on a collar 102' of the axis 102 (see figure 3). Thus, the rotor 3 rotates on itself around its central axis in front of the stator 2 which is fixed to it: during this movement of the rotor 3 in a circumferential direction, the main surfaces 3.1, 3.2 remain parallel to the main surfaces 2.1, 2.2. The attachment of the stator 2 to the collar 102' allows the stator 2 to be movable in sliding without rotation in an axial direction of the shaft 102 between a braking position and a position of free rotation of the wheel 103. In its braking position, the stator 2 is brought closer to the rotor 3 to the point that the second main surface 2.2 of the stator 2 is engaged in the second main surface 3.2 of the rotor 3: the main surfaces 2.1, 3.1 are separated from each other by a first predetermined air gap and the main surfaces 2.2, 3.2 are separated from each other by asecond predetermined air gap. In its free rotation position, the stator 2 is spaced from the rotor 3 to the point that the second main surface 2.2 of the stator 2 is clear of the second main surface 3.2 of the rotor 3: the main surfaces 2.1, 3.1 are separated from each other by a third predetermined air gap and the main surfaces 2.2, 3.2 are separated from each other by a fourth predetermined air gap. In a manner known per se, at least one linear electromechanical actuator, not shown here, controllable by the pilot of the aircraft, moves the stator 2 between the two aforementioned positions. The arrangement of the magnets is shown in Figure 6. The magnets, here based on rare earths, are for example 16 in number and are fixed to the crown of the stator 2 possibly via a magnetic steel support, or even on a non-magnetic support. The magnets of each series here comprise first magnets 11, 13 having a first vector ofmagnetization substantially perpendicular to the main surface 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 angular sector shapes and 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: - each magnet 11 has its magnetization vector which leaves the main face 2.1 (its North pole opens onto the main face 2.1), - each magnet 12 hasits magnetization vector which extends from the neighboring magnet 11 to 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 to the neighboring magnet 13. 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. 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 whose mass can be reduced since it does not need to ensure a magnetic flux conduction function. The arrangement of the magnets 11, 12, 13, 14 is the same on the main surfaces 2.1, 2.2. It is understood that to cause braking, the actuatorselectromechanical control actuators are controlled to bring the stator 2 into the braking position and that, to interrupt the braking, the electromechanical control actuators are controlled to bring the stator 2 into the free rotation position in which the rotor 3, and therefore the wheel 103, can rotate freely. In the braking position, the magnets generate eddy currents in the rotor 3 sufficient to generate a braking force on the rotor 3. The circulation of the eddy currents in the rotor 3 tends to cause heating of the rotor 3, all the more so when these currents have a high intensity. However, it is necessary to limit the heating of the rim portion 105.1 in the vicinity of the tire in order to limit the heating of the tire which could result therefrom. The rotor 3 in which the eddy currents circulate is therefore designed to have a sufficient volume to store the heat released during braking. In addition,the connecting ring 4 has a cross-section (in a plane perpendicular to the axis of rotation of the wheel 103), here relatively thin and smaller than that of the rotor 3, which defines a restricted passage section for the heat towards the rim part 105.1. The holes 5 make it possible to further limit this passage section so that the braking heat can only be evacuated in a very limited way by conduction towards the rim part 105.1. In addition, the holes 5 increase the exchange surface of the connecting ring 4 with the ambient air. The heat will therefore be evacuated from the rotor 3 by radiation, by contact with the air flow flowing over the rotor 3 due to the movement of the wheels and the aircraft and also by conduction towards the rest of the wheel. In the free rotation position, the magnets do not allow sufficient eddy currents to be generated in the rotor 3 to cause braking of the rotor 3. It will be noted that below a certain speed ofrotation of the rotor 3, the braking torque is negligible regardless of the position of the stator 2. It will then be necessary to consider an additional brake. In this first embodiment, the annular space provided between the hub part 104.1 and the rim part 105.1 is free and can accommodate a stack of stator and rotor discs of a conventional friction brake. The rim part 105.1 would for this purpose be provided internally with axial ribs 108.1 serving to connect the rotor discs in rotation to the wheel and a torque tube connected to the shaft 102 would itself be provided externally with axial ribs serving to connect the stator discs in rotation to the shaft 102. The friction brake conventionally comprises a plurality of hydraulic or electromechanical actuators carried by an actuator holder secured to the torque tube. For example, each electromechanical actuator comprises an electric motor and a pusher capable of being moved by the motor.electric 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. It is noted that, in this embodiment with friction brake, the discs serve as heat sinks and further limit the risk of heat transfer from the rotor to the tire. Elements identical or similar to those previously described will bear a numerical reference identical to these in the following description of the second and third embodiments of the invention with reference to FIGS. 4 and 5. In these two embodiments, the rotor 3 extends in the annular space formed between the hub part 104.1 and the rim part 105.1 and has a tubular shape of circular section. The rotor 3 extends here substantially from the lip 107.1 to the web part 106.1 without touching the latter. THErotor 3 has a cylindrical internal surface forming its main surface 3.2 and is fixed from the outside to the internal surface of the half-rim 105.1 by means of one or more connecting elements 4', 4'' depending on the embodiment. These connecting elements 4', 4'' are in a single piece with the half-wheel 103.1. The stator is not shown in these figures but comprises at least one axial tubular part provided with magnets and defining an external cylindrical main surface intended to be engaged in the rotor 3 opposite the main surface 3.2. Optionally, the stator may also comprise a radial part provided with magnets and intended to extend opposite the front annular face of the rotor (the annular face of the rotor 3 closest to the lip 107.1). The connecting elements 4', 4'' connecting the outside of the rotor 3 to the inner surface of the rim part 105.1 will now be described. According to the second embodiment, theconnecting elements 4' comprise annular fins extending circumferentially around the rotor 3 having an inner periphery secured to the rotor 3 and an outer periphery secured to the rim portion 105.1. The annular fins 4' are distributed along the length of the rotor 3 and are pierced with holes 5 which make it possible to limit the mass of the wheel and to increase the exchange surface with the ambient air. The wheel portion 103.1 according to the second embodiment is preferably produced by additive manufacturing. According to the third embodiment, the connecting element 4'' is a single, relatively thick annular wing extending circumferentially around the rear end of the rotor 3 (the one adjacent to the sail portion 106.1) having an internal periphery secured to the rotor 3 and an external periphery secured to the rim portion 105.1. An annular space 6 is provided between the rotor 3 and the internal surface of the rim portion 105.1 forlimit the mass of the wheel. The wheel part 103.1 according to the third embodiment is preferably made of casting. It is understood that, in all embodiments, the rotor 3 is in one piece with the wheel part 103.1 and that the half-wheel 103.1 serves in whole or in part as a heat sink, taking care to avoid heat transfer to the tire. The rotor 3, the ribs 108.1 and the annular wing 4'' are relatively large: their volume is determined to give them sufficient thermal capacity to form a massive heat storage part limiting the risk of heat transfer to the tire. The pierced annular fins 4' will, for their part, promote heat dissipation by the air circulating around the rotor 3. 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, thewheel may have a structure different from that described. A rim portion (serving as a support for the tire) may be attached to a web portion and / or a web portion may be attached to a hub portion. Instead of being formed from two half-wheels, the wheel may be a single piece, made by casting or by additive manufacturing. The wheel may be made of any electrically conductive material having mechanical properties compatible with the intended application. The shape, arrangement and dimensions of the magnets may be different from those described. For example, the magnets 11, 12, 13, 14 may be identical to each other or occupy different surfaces by having different widths and / or lengths. It is not mandatory to use a Halbach pattern. The magnetic braking device may be axial flux (the rotor and the stator have only radial surfaces as their main surfaces), radial flux (the rotor andthe stator have as main surfaces only axial surfaces as in figures 4 and 5) or combine axial and radial flows (the rotor and the stator have axial and radial main surfaces as in figures 2 and 3). The invention applies to any rotor formed from a tubular portion in a single piece with the rim part. Thus, it is understood that in the embodiments described, the rotor 3 comprises a tubular portion extending in projection from the rim part 105.1 either laterally (crown of figures 2 and 3) or towards the axis of rotation of the wheel (tube of figures 4 and 5). Generally speaking, the actuators can be electromechanical, hydromechanical or hydraulic actuators, single or double acting. For a single acting actuator, the power supply allows a forward movement of the pusher and an elastic element allows the return of the pusher. The number of actuators may be different from that mentioned. Preferably,at least three actuators will be used symmetrically distributed around the axis of rotation of the wheel to balance the axial forces exerted on the stators. Other modes of actuation of the magnetic brake are possible: for example electromagnetic by means of coils generating a magnetic field canceling that of the permanent magnets, rotors and stators being axially fixed. The invention can be used on any type of vehicle comprising a landing gear.

Claims

CLAIMS 1. Landing gear (101) comprising a leg having one end carrying a shaft (102) on which a wheel (103) is mounted, the wheel (103) comprising at least one hub portion (104.1) and a rim portion (105.1) coaxial with the hub portion (104.1) and connected to the hub portion (104.1) by a sail portion (106.1), the wheel comprising an eddy current magnetic braking device (1) comprising a rotor (3) rotatably connected to the wheel and a stator (2) which is rotatably connected to the leg and rotatable relative to the rim portion (105.1) and to the rotor (3) and which carries a plurality of magnets (11, 12, 13, 14) capable of emitting a magnetic flux generating eddy currents in the rotor (3), made of electrically conductive material, when the stator (2) and the rotor (3) are opposite each other and in relative motion, characterized in that the rotor (3) is in one piece with the rim part (105.1). 2.Landing gear according to claim 1, wherein the rotor (3) and the stator (2) have radial surfaces (3.1, 2.1) facing each other and the magnets (11, 12, 13, 14) are positioned on the stator (2) to emit a magnetic field between these surfaces parallel to a central axis of the wheel (103).

3. Landing gear according to claim 1 or 2, wherein the rotor (3) comprises a crown extending laterally with respect to a lip (107.1) of the rim portion (105.1) and connected to said rim portion (105.1) by a connecting portion, the connecting portion having a cross-section smaller than a cross-section of the crown of the rotor (3).

4. Landing gear according to claim 1, wherein the rotor (3) and the stator (2) have axial surfaces (3.2, 2.2) facing each other and the magnets (11,. 12, 13, 14) are positioned on the stator (2) to emit a magnetic field between these surfaces perpendicular to a central axis of the wheel (103).

5. Landing gear according to claim 4, wherein the rotor (3) comprises a tube which is coaxial with the hub portion (104.1) and extends between the rim portion (105.1) and the hub portion (104.1), the tube has an inner surface forming the axial surface (3.2) of the rotor (3).

6. Landing gear according to claim 1, wherein the rotor (3) and the stator (2) have first radial surfaces (3.1, 2.1) facing each other and the magnets (11, 12, 13, 14) comprise first magnets positioned on the stator (2) to emit a magnetic field between the first surfaces (3.1, 2.1) parallel to a central axis of the wheel (103) and wherein the rotor (3) and the stator (2) also have second axial surfaces (3.2, 2.2) facing each other and the magnets (11, 12, 13, 14) comprise second magnets positioned on the stator (2) to emit a magnetic field between the second surfaces (3.2, 2.2) perpendicular to a central axis of the wheel (103).

7. Landing gear according to any one of the preceding claims, comprising solid parts (108.1) for storing heat in the vicinity of the rotor (3), said solid parts being in one piece with the rim part (105.1).

8. Landing gear according to any one of the preceding claims, wherein the rotor (3) comprises a tubular portion extending projecting from the rim part (105.1).

9. Landing gear according to any one of the preceding claims, in which the magnets (11, 12, 13, 14) are arranged in a Halbach pattern.

10. Aircraft comprising a structure on which is mounted at least one landing gear according to any one of the. previous claims.

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