Braking system with locking apparatus, and associated landing gear, aircraft and control method

Abstract

The invention relates to an electromechanical braking system comprising a stack of disks (15) and an actuator, the actuator comprising at least a motor (17) and an actuating member connected to the motor and comprising a locking apparatus (20) for locking the actuating member. According to the invention, the locking apparatus comprises a frame (21), a movable part (22) able to move relative to the frame, the movable part being connected to the actuating member, the frame defining a chamber internal to the locking apparatus inside which at least a portion of the movable part is arranged, the chamber being filled with a magnetorheological fluid, the locking apparatus also comprising a magnetic device which has a coil (40), an activation and / or a deactivation of the coil making it possible to modify the behavior of the magnetorheological fluid. The invention also relates to a landing gear, an aircraft and a corresponding control method. FIGURE FOR THE ABSTRACT: Fig. 3

Description

[0001] Description

[0002] Title of the invention: Braking system with locking device, landing gear, aircraft and associated piloting method

[0003] The invention relates to an electromechanical braking system, said system being equipped with a locking device.

[0004] The invention also relates to a lander equipped with such a braking system.

[0005] The invention also relates to an aircraft equipped with such a braking system.

[0006] The invention also relates to a method for controlling such a locking device.

[0007] BACKGROUND OF THE INVENTION

[0008] An aircraft wheel typically consists of a rim fitted with a tire and connected by a flange to a hub mounted to rotate on a wheel-supporting shaft (axle or spindle). Friction braking devices are known to include a stack of brake discs housed in an annular space extending between the rim and the hub. These discs alternate between rotor discs, which rotate with the wheel, and stator discs, which are fixed relative to the wheel-supporting shaft. The braking device also includes electromechanical actuators mounted on an actuator carrier and arranged to apply a pressing force to the stack of discs, thereby generating a braking torque to slow the wheel's rotation.

[0009] When the aircraft is stationary, it is also possible to keep the wheel locked in position relative to the shaft by maintaining pressure on the same braking device. Unfortunately, the rotor and stator discs tend to wear out quickly, requiring regular replacement.

[0010] In addition, the friction of these discs generates particularly polluting dust particles.

[0011] Furthermore, the electromechanical actuators must remain powered to maintain the pressing force, which is energy-intensive.

[0012] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by different countries. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively contributing to the fight against climate change for several years now. Technological research efforts have already led to significant improvements in the environmental performance of aircraft.The Applicant takes into consideration the factors impacting all phases of design and development in order to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

[0013] Consequently, the Applicant is constantly working to reduce its negative climate impact by employing environmentally sound methods and processes for development and manufacturing that minimize greenhouse gas emissions to the absolute minimum possible, thereby reducing the environmental footprint of its activities. This sustained research and development work focuses on new generations of aircraft engines, aircraft weight reduction (particularly through the use of lighter materials and onboard equipment), the development of electric propulsion technologies, and, as essential complements to technological progress, aviation biofuels.

[0014] SUBJECT OF THE INVENTION

[0015] The invention aims in particular to provide an electromechanical braking system that reduces the environmental impact of the associated vehicle.

[0016] SUMMARY OF THE INVENTION

[0017] For this purpose, an electromechanical braking system is provided comprising a stack of discs and at least one electromechanical actuator, the actuator comprising at least one electric motor and at least one actuating member linked to the motor and capable of applying a force to the stack of discs, the actuator comprising at least one locking device for the actuating member.

[0018] According to the invention, the locking device comprises a frame, a movable part relative to the frame, the movable part being linked to the actuating member, the frame delimiting at least one internal chamber of the locking device in which at least a portion of the movable part is arranged, said chamber being filled at least in part with at least one magnetorheological fluid, the locking device also comprising at least one magnetic device comprising at least one coil, an activation and / or deactivation of the coil allowing to modify the behavior of the magnetorheological fluid.

[0019] Thus, when the magnetic device is activated (i.e. at least one electric current passes through its coil) and / or deactivated (i.e. no electric current passes through the coil), it modifies at least one characteristic of the magnetorheological fluid, such as its viscosity.

[0020] Consequently, depending on the magnetic field emitted by the magnetic device, the magnetorheological fluid can be:

[0021] - very viscous. In this case, the moving part becomes locked in position relative to the frame. fluid. In this case, the movement of the moving part relative to the frame is free.

[0022] By modifying the magnetic field emitted by the magnetic device, it is thus possible to make the magnetorheological fluid pass from one state to another in a reversible manner.

[0023] The invention therefore makes it possible to temporarily couple the moving part and the frame of the locking device.

[0024] The invention therefore makes it possible to lock and block the actuation member in position (in particular with respect to the stack of discs) by means of the locking device.

[0025] Optionally, the locking device is connected to the actuating member via at least one reduction assembly.

[0026] Optionally, a first reduction unit is arranged between the actuation member and the motor and a second reduction unit is arranged between the motor and the locking device.

[0027] Optionally, the moving part includes at least one drum and at least one output shaft extending from the drum.

[0028] Optionally, the drum includes at least one wall extending into a groove in the frame, forming at least part of the chamber.

[0029] Optionally, the magnetic device also includes at least one magnet.

[0030] Optionally, the magnet is a programmable magnet. Optionally, the magnet surrounds the coil. The invention relates to an aircraft landing gear comprising a system such as the one described above.

[0031] The invention also relates to an aircraft comprising a landing gear as described above.

[0032] The invention also relates to a method of controlling a system such as the one mentioned above, to lock the moving part with respect to the frame when the actuating member applies a force on the stack of discs, the method comprising at least the step of, following a locking command of the moving part in the frame, supplying the coil or ceasing to supply the coil in order to modify the magnetic field generated by the magnetic device, with respect to a magnetic field generated by the magnetic device before the locking command, and thus increase the viscosity of the magnetorheological fluid.

[0033] The invention also relates to a method for controlling an electromechanical braking system as described above, in which the magnetic device also includes a programmable magnet, the method for locking and unlocking the moving part relative to the frame, the method comprising at least the steps of:

[0034] - Following a locking command for the moving part in the frame, power the coil to activate the magnet, the magnet then generating a magnetic field to increase the viscosity of the magnetorheological fluid, then stop powering the coil,

[0035] - following an order to unlock the moving part in the frame, power the coil to deactivate the magnet, the magnet then ceasing to generate a magnetic field thus reducing the viscosity of the magnetorheological fluid, then stop powering the coil.

[0036] With such a process, the system can thus play the role of a parking brake: it is enough, in fact, to transmit the locking order when the actuation member applies a force on the stack of discs.

[0037] Advantageously, such a process and system prove to be relatively energy-efficient, the coil being activated only occasionally to program or deprogram the magnetization of the magnet.

[0038] Other features and advantages of the invention will become apparent from the following description of particular and non-limiting embodiments of the invention.

[0039] BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Reference will be made to the attached drawings, among which: [Fig. 1] Figure 1 is a simplified representation of an aircraft according to a first embodiment of the invention; [Fig. 2] Figure 2 is a partial schematic view of a landing gear of the aircraft shown in Figure 1, in half axial section;

[0041] [Fig.3] Figure 3 is a schematic cross-sectional view of part of a braking system associated with the 'lander shown in Figure 2;

[0042] [Fig. 4] Figure 4 is a cross-sectional view of a locking device for the braking system illustrated in Figure 3

[0043] [Fig. 5] Figure 5 is an enlarged view of part of the device shown in Figure 4, when no magnetic field is generated by said device;

[0044] [Fig. 6] Figure 6 is an identical view to that of Figure 5, when a magnetic field is generated by the locking device 20;

[0045] [Fig. 7] Figure 7 is a variant arrangement of the part of the braking system associated with the lander shown in Figure 2; [Fig. 8] Figure 8 is a diagram of a first possible piloting of the locking device 20 shown in Figure 4,

[0046] [Fig. 9] Figure 9 is a diagram of a second possible control method for the locking device 20 shown in Figure 4,

[0047] [Fig. 10] Figure 10 is a cross-sectional view of a locking device for an aircraft braking system according to a second embodiment of the invention.

[0048] DETAILED DESCRIPTION OF THE INVENTION

[0049] Figure 1 represents an aircraft 100 comprising landing gear 101 according to a first embodiment.

[0050] At least one of the landers 101 includes a leg having an end here provided with two coaxial shafts 102 on each of which is mounted to pivot at least one wheel 103, each shaft 102 having a central axis defining an X axis of rotation of the wheel 103 which it carries.

[0051] With reference to Figure 2, at least one of the wheels 103 is mounted for rotation on the associated shaft 102 via bearings 3.

[0052] The wheel 103 is equipped with an electromechanical braking system F comprising a stack of discs 15 made up of rotors 4 which are mobile in rotation with the wheel 1 by means of a peripheral key 5. Alternating with the rotors 4 are arranged stators 6, the stators 6 being linked in rotation to a torsion tube 7 by means of an internal key 8.

[0053] The torsion tube 7 is for example screwed to a ring 9 which is threaded onto the shaft 102 and stopped in rotation relative to it so that the stators 6 are immobile in rotation relative to the shaft 102.

[0054] The crown 9 carries circumferentially arranged electromechanical actuators 10, only one of which is shown here in figure 2.

[0055] The different actuators 10 are, for example, identical to each other, so that the following description of one of the actuators 10 is also applicable to the other actuators 10.

[0056] With reference to figures 3 to 6, the actuator 10 includes a housing 11 which is attached to the ring 9 and is preferably fixed to said ring 9.

[0057] The actuator 10 also includes at least one actuating element capable of applying force to the stack of discs. The actuating element thus comprises at least one screw 13, rotatably mounted in the housing 11, and at least one nut 12 that cooperates with said screw 13. The nut 12 is prevented from rotating relative to the housing 11 by an anti-rotation device. The screw 13 and the nut 12 thus cooperate so that a rotation of the screw 12 causes an axial displacement of the nut 12. The nut 12 terminates in a pusher 16. The pusher 16 extends out of the housing 11. The screw 13, and at least a portion of the nut 13, extend into the housing 11.

[0058] Furthermore, the actuator 10 includes at least one electric motor 17. Said motor 17 is, for example, arranged at least partly inside the housing 11 and / or arranged at least partly outside the housing 11. In the present case, the motor 17 is arranged entirely inside the housing 11.

[0059] The motor 17 has an output shaft 18 equipped with at least one pinion.

[0060] According to one possibility, the said pinion directly drives the screw 13 in rotation.

[0061] According to a second possibility, the pinion drives the screw 13 via a reduction gear 14, which establishes a kinematic link between the screw 13 and the electric motor 17. The reduction gear 14 may thus comprise one or more reduction stages. The reduction gear 14 is, for example, arranged at least partially inside the housing 11 and / or arranged at least partially outside the housing 11. In the present case, the reduction gear 14 is entirely contained within the housing 11.

[0062] The actuator 10 also includes a locking device 20 for the actuating member. The locking device 20 is, for example, arranged at least partly inside the housing 11 and / or arranged at least partly outside the housing 11 and / or arranged at least partly outside the housing 11. In the present case, the locking device 20 is arranged entirely within the housing 11.

[0063] The locking device 20 comprises a frame 21 and a moving part 22 mounted movably within the frame 21. In this case, the moving part 22 is mounted movably to rotate about at least one Y axis. In this case, the moving part 22 is only mounted movably to rotate within the frame 21 about a single Y axis.

[0064] Said Y axis is preferably parallel to the axis of rotation of the output shaft 18. Said Y axis may or may not coincide with said axis of rotation of the output shaft 18.

[0065] Optionally, the moving part 22 is adapted to cooperate directly with the motor 17 so that the output shaft 18 is directly rotationally linked to an output shaft 23 of the moving part 22. For example, the two shafts 18 and 23 are coupled directly together or via a gear pair. In both cases, no reduction gear unit connects the output shaft 18 of the motor 17 to the output shaft 23 of the locking device 20. The two shafts 18 and 23 can optionally be one piece.

[0066] Optionally, the locking device 20 is arranged in the vicinity of the motor 17. The locking device 20 is, for example, arranged in line with the motor 17.

[0067] In the illustrated embodiment, the Y axis coincides with the motor output shaft.

[0068] The locking device 20 is designed to lock the actuating member in position relative to the housing 11. In the illustrated example, it actually first locks the output shaft 18 in position and therefore, consequently, locks the actuating member in position via the reduction gear assembly 14. This is only one alternative, and it is understood that the locking device 20 can lock the actuating member in position by acting on a component of the kinematic linkage further downstream of the kinematic linkage between the motor 17 and the actuating member. The locking device 20 can thus act, for example, directly on the screw 13, the nut 12, or the shaft 18 itself.

[0069] The locking device 20 is, for example, configured to allow the actuating member to be locked in position at least in the event of a power failure to supply the motor 17. The locking device 20 is, for example, configured to provide at least a parking brake function (better known by the English term "park brake").

[0070] We will now turn our attention to the description of the locking device 20.

[0071] The moving part 22 includes the aforementioned output shaft 23 and a drum 25 extending from said output shaft 23, the drum 25 thus being rotationally fixed to the output shaft 23. This drum 25 may be one piece with the output shaft 23 or may be fixed to the output shaft 23.

[0072] The drum 25 preferably includes a portion for attaching to the output shaft 23, extended by a working portion. The attachment portion is, for example, in the form of a cylindrical bell with a circular cross-section, formed by a bottom 26 and a side wall 27 extending from the bottom 26. The bell thus has a U-shape. The output shaft 23 is, for example, fixed to the bottom 26 and thus extends inside the bell. Alternatively, the output shaft 23 is fixed to the center of the bottom 26, with the output shaft 23 and the bell extending coaxially with each other and with the Y-axis. Optionally, the free end of the side wall 27 (opposite to the end attached to the bottom 26) is extended by a peripheral rim 28. This rim 28 is, for example, in the form of a ring with a circular cross-section. The border 28 thus extends coaxially to the Y axis. The border 28 extends outwards from the bell.

[0073] The work portion includes at least one first wall

[0074] 29 extending from the edge 28 towards the bottom 26. Said first wall 29 is, for example, shaped into a closed ring with a circular cross-section. Said first wall 29 thus extends coaxially to the Y-axis. Said first wall 29 forms, for example, a peripheral rim to the edge 28 by extending its free end. The first wall 29 thus externally surrounds the lateral wall 27.

[0075] Preferably, the working portion includes a second wall 30 extending from the edge 28 towards the bottom 26. This second wall 30 is, for example, shaped as a closed ring with a circular cross-section. This second wall 30 thus extends coaxially with the Y-axis. This second wall 30 has a diameter smaller than that of the first wall 29 so that it is externally enclosed by the first wall 29. The second wall

[0076] 30 thus surrounds the lateral wall 27 externally. The first wall 29 and the second wall 30 have an identical height (along the Y axis).

[0077] Furthermore, the frame 21 includes at least one base 32 and a cover 33 closing the base 32. The frame 21 extends coaxially to a given axis which is here coincident with the Y axis of the output shaft 23. The frame 21 thus extends coaxially to the output shaft 23 and to the moving part 22.

[0078] The moving part 22 is therefore entirely arranged inside the frame 21, except for a portion of the output shaft 23 which remains arranged outside the frame 21.

[0079] In particular, the base 32 is suitable for accommodating the bell of the movable part 22 and in particular its bottom 26 and its side wall 27.

[0080] Preferably, the base 32 has a floor 42 offset from a bottom 43 of the base 32. The floor 42 and the bottom 43 define a sealed (here annular) space. The floor 42 is fixed to the base 32 and, in particular, to a lateral wall of said base 32. This space can also be called an expansion chamber 45.

[0081] Optionally, the frame 21 includes a sleeve 34 extending between the base 32 and the cover 33. The sleeve 34, the base 32, and the cover 33 are fixed to each other. The sleeve 34 surrounds the side wall 27 externally. The sleeve 34 forms a junction of the frame 21 between the base 32 and the cover 33.

[0082] The border 28 thus extends between the cover 33 and the sleeve 34.

[0083] Furthermore, the sleeve 34 has a first groove 35 within which the first wall 29 extends, and a second groove 36, coaxial with the first groove 35, within which the second wall 30 extends. Each of the grooves 35 and 36 thus forms a chamber of the frame 21. At least one of the chambers, and preferably both chambers, are filled at least partially with at least one magnetorheological fluid—hereafter referred to as MR fluid. In this case, the same MR fluid fills both chambers. The two chambers may optionally be connected to each other so that the MR fluid can flow from one chamber to the other.

[0084] In this case, the two chambers are in communication so that the MR fluid can circulate from one chamber to the other.

[0085] Preferably, all the available space (including the two aforementioned chambers) between the drum 25 and the delimited housing in the frame 21, a housing defined between the cover 33 and the base 32, is filled with said fluid MR. All this space (including the two aforementioned chambers) thus forms a general chamber internal to the frame 21.

[0086] The said general chamber is sealed so that the MR fluid remains confined within said general chamber. Said general chamber is arranged so as to be able to be subjected to at least one magnetic field generated by at least one magnetic device, which will be described below.

[0087] We choose here an MR fluid which is fluid when not subjected to any magnetic field and which becomes viscous in the presence of a magnetic field.

[0088] Advantageously, the main chamber has a shape corresponding to that of the drum 25 arranged within it. This reduces the amount of MR fluid required to brake the moving part 22 within the frame 21.

[0089] Advantageously, the walls 29, 30 are completely immersed in the MR fluid. More specifically, the inner and outer faces of said walls 29, 30 are in contact with the MR fluid.

[0090] The output shaft 23 passes through the cover 33 and enters the frame 21 such that one end is arranged outside the frame 21 and the other end is arranged inside the frame 21. One or more bearings 37 are arranged between the output shaft 23 and the frame 21. This allows the output shaft 23 to rotate about the Y-axis within the frame 21. Preferably, the locking device 20 also includes at least one sealing element 38 associated with the output shaft 23. For example, the sealing element 38 is arranged between the output shaft 23 and the cover 33. For example, the cover 33 has a cylindrical side wall 39 extending inside the bell and / or sleeve 34, with the output shaft 23 extending inside said cylindrical side wall 39 coaxially with said wall. Said cylindrical side wall 39 carries for example the bearing(s) 37 and / or the sealing element 38.

[0091] In service, the working portion interacts with the MR fluid so that the rotation of the moving part 22 can be more or less slowed down by the MR fluid depending on its viscosity, defined by the magnetic field generated by the magnetic device.

[0092] A first possible magnetic device will now be described.

[0093] In this first possibility, the magnetic device includes at least one means capable of generating a permanent magnetic field. This means is, for example, a permanent magnet 41. The magnet 41 is, for example, shaped like a disc. The magnet 41 is, for example, located inside the sleeve 34. The magnet 41 thus externally surrounds the drum bell 25 and / or the base 32. Preferably, the magnet 41 externally surrounds the coil 40.

[0094] Furthermore, the magnetic device also includes at least one means capable of generating a magnetic field temporarily. This means is specifically configured to generate a magnetic field that will oppose that of magnet 41 and preferably one that will cancel out the magnetic field generated by magnet 41 when said means is activated.

[0095] In this way, the activation (as well as the deactivation) of said means will allow the viscosity of the MR fluid to be varied.

[0096] The means is, for example, a coil 40. The coil 40 is, for example, arranged inside the sleeve 34. The coil 40 thus surrounds the outer part of the drum bell 25 and / or the base 32. The coil 40 thus extends coaxially to the Y-axis. The coil 40 preferably has a diameter greater than that of the first wall 29 and / or the second wall 30. The coil 40 extends, for example, opposite the first wall 29 and / or the second wall 30.

[0097] At least part of the frame 21 is made of a material capable of conducting a magnetic field. For example, at least part of the frame 21 is made of a ferromagnetic material. In this case, at least the sleeve 34 is made of a ferromagnetic material. Thus, the magnetic permeability of the general chamber is increased, improving the conduction of the magnetic field.

[0098] From then on, the field lines of the magnet 41 pass through the sleeve 34 and then the two chambers and close on the magnet 41. When the coil 40 is energized, its field lines follow the reverse path of the magnetic field lines of the magnet 41.

[0099] Preferably, the cover 33 and the base 32 are made of non-magnetic material to prevent dispersion of the magnetic field lines. Preferably, at least one pad 44 made of non-magnetic material is arranged between the coil 40 and the grooves 35, 36. This pad 44 thus limits the risk of dispersion of the magnetic field lines.

[0100] The pad 44 is thus positioned inside the sleeve 34. The pad 44 thus surrounds the outer part of the drum bell 25 and / or the base 32. The pad 44 extends coaxially with the Y-axis. The pad 44 preferably has a diameter greater than that of the first wall 29 and / or the second wall 30. The pad 44 extends, for example, opposite the first wall 29 and / or the second wall 30. Said pad 44 is, for example, shaped into a ring. The coil 40 is connected to an electrical power supply (not shown) controlled by a control device 50 of the braking system F in order to vary at least the current flowing through the coil 40.

[0101] Preferably, the braking system F also includes at least one sensor 51 capable of measuring at least one representative value of the magnetic field generated by the coil 40. For example, the sensor 51 is a sensor for measuring the electric current flowing through the coil 40.

[0102] Optionally, the locking device 20 includes a substrate 46 comprising at least the sensor 51 and / or includes at least one element providing the coil 40 with electrical power (said element receiving electrical power from the source) and / or includes an internal control element within the locking device (controller for example) and / or includes at least one other sensor than the sensor 51 (temperature sensor of the coil 40, temperature sensor of the fluid MR, ...) and / or includes at least one element receiving commands from the control element 50, etc.

[0103] The substrate 46 is, for example, a printed circuit board. The substrate 46 is preferably supported by the frame 21. The substrate 46 is, for example, supported by the sleeve 34. The substrate 46 is, for example, entirely arranged within the sleeve 46. The substrate 46 is, for example, arranged within the sleeve 34 near the coil 40.

[0104] We will now describe the operation of the braking system F with this first possibility of the magnetic device.

[0105] In operation, when the coil 40 is not energized, only the magnet 41 generates a magnetic field: this magnetic field makes the fluid MR highly viscous. The high viscosity of the fluid MR then prevents relative rotation between the working portion of the drum 25 and the frame 21. As a result, the output shaft 23 of the locking device 20 is also locked in position relative to the frame 21. Consequently, the output shaft 18 of the motor 17, and therefore the nut 12, are also prevented from rotating.

[0106] Furthermore, in the absence of a braking order, the pusher 16 is offset from the stack of discs 15. The stator discs thus rotate freely relative to the rotor discs, allowing free rotation of the wheel 103 around its shaft 102.

[0107] During a braking command, coil 40 is energized. Energizing of coil 40 occurs simultaneously with the braking command and / or after a specified time interval following this braking command.

[0108] This results in a change in the magnetic field generated by the magnetic device (corresponding to the combination of the magnetic field generated by the permanent magnet and that generated by the coil 40). For example, the magnetic field of the coil 40 cancels out that of the magnet 41, so that the magnetic field generated by the magnetic device is zero or almost zero. This then leads to a decrease in the viscosity of the fluid MR. The moving part 22 can thus move relative to the frame 21. Consequently, the output shaft 18 of the motor 17, and therefore the nut 12, are free to rotate.

[0109] The electric motor 17 is then powered. Power to the motor 17 is supplied simultaneously with the braking command and / or after a specified time interval following this braking command and / or when the sensor 51 detects that the electrical current flowing through the coil 40 exceeds a certain threshold, etc. The electric motor 17 then drives the output shaft 18 to rotate. This causes an axial displacement of the screw 13: the pusher 16 thus cooperates with the stack of discs 15 to exert pressure on it in response to a torque imposed by the electric motor 17. The stator and rotor discs then rub against each other, causing the rotor discs to brake and then stop relative to the stator discs, and therefore the wheel 103 relative to the shaft 102.

[0110] If braking is to be stopped, the direction of rotation of the electric motor 17 is reversed so that the pusher 16 moves back relative to the stack of discs 15, and then the electric motor 17 is stopped. The coil 40 can then cease to be powered so that the fluid MR becomes viscous again.

[0111] If, on the other hand, it is desired to engage the parking brake (i.e., to keep the position of the push button 16 in contact with the stack of discs 15), a locking command is transmitted to the locking device 20. This command can be transmitted manually by the pilot or automatically by an on-board unit of the aircraft (for example, after a given time interval following the braking command and / or the shutdown of the propulsion engines, etc.).

[0112] The power supply to coil 40 is then stopped. The power supply to coil 40 is stopped simultaneously with the locking command and / or after a specified time interval following this locking command.

[0113] Furthermore, the power supply to motor 17 is stopped simultaneously with the locking command and / or after a given time interval after this locking command and / or when sensor 51 detects that the electrical current flowing through coil 40 exceeds (in absolute value) a certain threshold, etc.

[0114] Stopping the power supply to coil 40 causes a change in the magnetic field generated by the magnetic device, which in turn leads to an increase in the viscosity of fluid MR, since the permanent magnetic field generated by magnet 41 remains. This increase in the viscosity of fluid MR prevents relative rotation between the working portion of the drum 25 and the frame 21. Consequently, the output shaft 23 of the locking device 20 is also locked in position relative to the frame 21. As a result, the output shaft 18 of the motor 17, and therefore the nut 12, are also prevented from rotating. Therefore, the wheel 103 is no longer free to move relative to its shaft 102, even without the motor 17 needing to be powered. The parking brake is thus activated.

[0115] Advantageously, with this first option, coil 40 does not need to be powered when the parking brake is active.

[0116] It is noted that the expansion chamber 45 limits a risk of internal damage to the locking device 20 which could be caused by the expansion of the MR fluid (in case of temperature change for example).

[0117] If it is desired to be able to move the wheel 103 relative to the shaft 102 again, an unlocking command is transmitted to the locking device 20. This command can be transmitted manually by the pilot or automatically by the aircraft's onboard unit. The coil 40 is then re-energized so that its magnetic field cancels out that of the magnet 41. The energizing of the coil 40 occurs simultaneously with the unlocking command and / or after a specified time interval following this unlocking command.

[0118] The MR fluid becomes fluid again, and the moving part 2 can thus move relative to the frame 21. Consequently, the output shaft 18 of the motor 17, and therefore the nut 12, are free to rotate. The parking brake is thus deactivated.

[0119] The motor 17 can then be activated so that it can move the pusher 16 back against the stack of discs 15. The power supply to the motor 17 is activated simultaneously with the unlock command and / or after a given time interval after this unlock command and / or when the sensor 51 detects that the electrical current flowing through the coil 40 exceeds a certain threshold, etc.

[0120] Once the push button 16 is retracted, the power supply to the coil 40 can optionally be stopped. The power supply to the coil 40 can be cut off after a specified time interval following the unlock command and / or depending on the position of the push button 16 relative to the stack of discs 15, etc.

[0121] It is understood that with this first possibility, the coil 40 only needs to be powered during the temporary phases when the pusher 16 needs to be moved relative to the stack of discs 15.

[0122] Preferably, the control unit 50 implements at least one control loop of the coil 40 to modify the magnetic field it generates and thereby be able to control the locking generated by the locking device 20.

[0123] Referring to Figure 8, the control loop is preferably a closed loop. For example, the control loop is a current control loop.

[0124] For example, the control unit 50 determines a reference value 52 of an electrical supply intensity of the coil 40 enabling the coil 40 to generate a magnetic field totally or partially canceling the magnetic field of the magnet 41.

[0125] The control unit 50 can for example determine the reference value 52 from at least one conversion table 54 and at least one setpoint value 55 characteristic of a torque to be applied and / or a relative displacement between the moving part 22 and the frame 21.

[0126] The setpoint 55 can thus be a resisting torque to be applied to the output shaft 23 of the locking device 20 and / or to the output shaft 18 of the motor 17 and / or to the nut 12 and / or to a relative displacement between the moving part 22 and the frame 21, etc. This setpoint value 55 can be included in the (un)locking sequence and / or in the braking sequence and / or braking stop sequence and / or can be determined from one or more other parameters external to the locking device 20 (external temperature of the aircraft, speed of the aircraft, etc.) and / or can be determined from one or more other parameters internal to the locking device 20 (temperature of the MR fluid, temperature of the coil, etc.).

[0127] From there, the control unit 50 modifies at least one parameter of the electrical supply of the coil 40 so that an actual value 53 (the actual value 53 being transmitted for example by the sensor 51 to the control unit 50) reaches the reference value 52. Said parameter can be directly the electrical supply current of the coil 40 or a parameter related to this current.

[0128] A second possibility of the magnetic device will now be described.

[0129] In this second possibility, the magnetic device includes at least one means capable of generating a magnetic field in a controlled manner. This means is, for example, a programmable magnet 41. The magnet 41 is, for example, shaped like a disc. The magnet 41 is, for example, located inside the sleeve 34. The magnet 41 thus externally surrounds the drum bell 25 and / or the base 32. Preferably, the magnet 41 externally surrounds the coil 40.

[0130] Furthermore, the magnetic device also includes at least one means capable of generating a magnetic field temporarily. This means is specifically configured to generate a magnetic field that can both activate and deactivate magnet 41. When activated, magnet 41 behaves like a permanent magnet and thus generates a permanent magnetic field. When deactivated, magnet 41 no longer generates a magnetic field (or generates a magnetic field that is negligible compared to the magnetic field it generates when activated). In particular, when magnet 41 is deactivated, it has no influence on the viscosity of the MR fluid, unlike when magnet 41 is activated.

[0131] The means for temporarily generating a magnetic field is, for example, a coil 40. The coil 40 is, for example, arranged inside the sleeve 34. The coil 40 thus surrounds the outer part of the drum bell 25 and / or the base 32. The coil 40 thus extends coaxially to the Y-axis. The coil 40 preferably has a diameter greater than that of the first wall 29 and / or the second wall 30. The coil 40 extends, for example, opposite the first wall 29 and / or the second wall 30.

[0132] At least part of the frame 21 is made of a material capable of conducting a magnetic field. For example, at least part of the frame 21 is made of a ferromagnetic material. In this case, at least the sleeve 34 is made of a ferromagnetic material. Thus, the magnetic permeability of the general chamber is increased, improving the conduction of the magnetic field.

[0133] Therefore, when the magnet 41 is activated, the field lines of the magnet 41 pass through the sleeve 34 and then the two chambers and close on the magnet 41.

[0134] Preferably, the cover 33 and the base 32 are made of non-magnetic material to prevent dispersion of the magnetic field lines. Preferably, at least one pad 44 made of non-magnetic material is arranged between the coil 40 and the grooves 35, 36. This pad 44 thus limits the risk of dispersion of the magnetic field lines.

[0135] The pad 44 is thus positioned inside the sleeve 34. The pad 44 thus surrounds the outer part of the drum bell 25 and / or the base 32. The pad 44 extends coaxially with the Y-axis. The pad 44 preferably has a diameter greater than that of the first wall 29 and / or the second wall 30. The pad 44 extends, for example, opposite the first wall 29 and / or the second wall 30. Said pad 44 is, for example, shaped into a ring. The coil 40 is connected to an electrical power supply (not shown) controlled by a control device 50 of the braking system F in order to vary at least the current flowing through the coil 40.

[0136] Preferably, the braking system F also includes at least one sensor 51 capable of measuring at least one representative value of the magnetic field generated by the coil 40. For example, the sensor 51 is a sensor for measuring the electric current flowing through the coil 40.

[0137] Optionally, the locking device 20 includes a substrate 46 comprising at least the sensor 51 and / or includes at least one element providing the coil 40 with electrical power (said element receiving electrical power from the source) and / or includes an internal control element within the locking device (controller for example) and / or includes at least one other sensor than the sensor 51 (temperature sensor of the coil 40, temperature sensor of the fluid MR, ...) and / or includes at least one element receiving commands from the control element 50, etc.

[0138] The substrate 46 is, for example, a printed circuit board. The substrate 46 is preferably supported by the frame 21. The substrate 46 is, for example, supported by the sleeve 34. The substrate 46 is, for example, entirely arranged within the sleeve 46. The substrate 46 is, for example, arranged within the sleeve 34 near the coil 40.

[0139] We will now describe the operation of the braking system F with this second possibility of the magnetic device.

[0140] In operation, the magnet 41 generates no magnetic field and the coil 40 is not energized. Therefore, no magnetic field is generated by the magnetic device. As a result, the fluid MR remains fluid. The moving part 22 can thus move relative to the frame 21. Consequently, the output shaft 18 of the motor 17, and therefore the nut 12, are free to rotate.

[0141] Furthermore, in the absence of a braking order, the pusher 16 is offset from the stack of discs 15. The stator discs thus rotate freely relative to the rotor discs, allowing free rotation of the wheel 103 around its shaft 102.

[0142] During a braking command, the electric motor 17 is energized. The motor 17 is energized simultaneously with the braking command and / or after a specified time interval following this braking command, etc. The electric motor 17 then drives the output shaft 18 to rotate. This causes an axial displacement of the screw 13: the pusher 16 thus cooperates with the stack of discs 15 to exert pressure on it in response to a torque imposed by the electric motor 17. The stator and rotor discs then rub against each other, causing the rotor discs to brake and then stop relative to the stator discs, and consequently, the wheel 103 relative to the shaft 102.

[0143] If it is desired to engage the parking brake (i.e. to keep the position of the push button 16 in contact with the stack of discs 15), a locking command is transmitted to the locking device 20. This command can be transmitted manually by the pilot or automatically by an on-board unit of the aircraft (for example, after a given time interval following the braking command and / or the shutdown of the propulsion engines, etc.).

[0144] Coil 40 is then energized. The energizing of coil 40 occurs simultaneously with the locking command and / or after a specified time interval following this locking command. Coil 40 is also energized for a specified time interval and / or the electrical current transmitted to coil 40 follows a function over time. Preferably, this function is a square wave. In this way, coil 40 carries an electrical current that defines a programming signal. The energizing of coil 40 occurs for a short period, such as a time interval of less than 100 milliseconds or, for example, less than 50 milliseconds.

[0145] This activates the magnet 41, which then generates a permanent magnetic field even after the power supply to the coil 40 is cut off. This magnetic field makes the MR fluid highly viscous. The high viscosity of the MR fluid prevents relative rotation between the working portion of the drum 25 and the frame 21. Consequently, the output shaft 23 of the locking device 20 is also locked in position relative to the frame 21. As a result, the output shaft 18 of the motor 17, and therefore the nut 12, are also prevented from rotating. Therefore, the temporary activation of the coil allows the behavior of the MR fluid to be modified.

[0146] Furthermore, the power supply to motor 17 is stopped simultaneously with the locking command and / or after a given time interval after this locking command and / or when sensor 51 detects that the electrical current flowing through coil 40 exceeds a certain threshold, etc.

[0147] Advantageously, with this second option, coil 40 does not need to be energized when the parking brake is engaged. Advantageously, coil 40 only needs to be energized for a shorter period of time than with the first option. In particular, coil 40 does not need to be energized during the braking phase (by pressing button 16 on the stack of discs 15).

[0148] It is noted that the expansion chamber 45 limits a risk of internal damage to the locking device 20 which could be caused by the expansion of the MR fluid (in case of temperature change for example).

[0149] If it is desired to be able to move the wheel 103 relative to the shaft 102 again, an unlock command is transmitted to the locking device 20. This command can be transmitted manually by the pilot or automatically by the aircraft's onboard unit. The coil 40 is then re-energized. The energizing of the coil 40 occurs simultaneously with the unlock command and / or after a specified time interval following this unlock command. Furthermore, the coil 40 is energized for a specified time interval and / or the value of the electrical current transmitted to the coil 40 follows a function over time. Preferably, this function is different from that of the programming signal. This function is, for example, a sinusoidal function or, for example, a damped sinusoidal function. In this way, the coil 40 carries an electrical current that defines a deprogramming signal.The coil 40 is energized for a short time, for example a time interval of less than 100 milliseconds and for example less than 50 milliseconds.

[0150] This results in the deactivation of the magnet 41, which ceases to generate a magnetic field even after the power supply to the coil 40 is stopped.

[0151] No magnetic field is then generated by the magnetic device. Thus, the MR fluid remains fluid. The moving part 22 can again move relative to the frame 21. Consequently, the output shaft 18 of the motor 17, and therefore the nut 12, are free to rotate. As a result, the temporary activation of the coil 40 allows the behavior of the MR fluid to be modified.

[0152] The parking brake is thus deactivated.

[0153] The motor 17 can then be activated so that it can move the pusher 16 back against the stack of discs 15. The power supply to the motor 17 is activated simultaneously with the unlock command and / or after a given time interval after this unlock command and / or when the sensor 51 detects that the electrical current flowing through the coil 40 exceeds (in absolute value) a certain threshold, etc.

[0154] Advantageously, with this second option, coil 40 does not need to be powered when the parking brake is not active.

[0155] Advantageously, coil 40 only needs to be energized for a shorter period of time than with the first possibility. In particular, coil 40 does not need to be energized when pusher 16 is retracted from the stack of discs 15 (once magnet 41 is deactivated).

[0156] Advantageously, the magnetic device is configured so that the moving part 22 can rotate freely relative to the frame 21 when the magnet is not active, which is particularly the case during the flight phases of the aircraft 1. Thus, the locking device 20 proves to be relatively safe because it does not prevent the braking of the aircraft 1 even in the event of failure of the coil 40 or of one or more elements supplying the coil 40.

[0157] Preferably, the control unit 50 implements at least one control loop of the coil 40 to modify the magnetic field it generates and thereby be able to control the locking generated by the locking device 20.

[0158] With reference to figure 9, the control loop is, for example, an open loop.

[0159] For example, the control unit 50 determines the electrical supply intensity signal to be transmitted to the coil 40, enabling the coil 40 to activate or deactivate the magnet 41.

[0160] The control unit 50 can, for example, determine the reference value 52 (related to the electrical supply intensity signal) from at least one conversion table 54 and at least one setpoint value 55 corresponding to a magnet activation command or a magnet deactivation command. The setpoint 55 can be directly the locking or unlocking command or can be representative of this command.

[0161] From this point, the control unit 50 modifies at least one parameter of the power supply to the coil 40 so that the electrical current flowing through the coil 40 forms the programming signal (here a square wave with a bounded time interval) or the deprogramming signal (here a sinusoid with a bounded time interval). This parameter can be directly the electrical current supplied to the coil 40 or a parameter related to this current.

[0162] Optionally, the actual value 53 of the power supply parameter for coil 40 can be measured by sensor 51. Optionally, the control unit 50 can thus determine whether the programming and / or deprogramming signal is being correctly followed. Optionally, the control unit 50 can also modify the power supply parameter for coil 40 so that the actual value 53 reaches the reference value 52. The control loop is then a closed control loop.

[0163] A reliable locking device has thus been described.

[0164] In addition, this locking device 20 is relatively compact and / or relatively lightweight.

[0165] Moreover, this locking device 20 is relatively easy to design.

[0166] In addition, the locking device 20 does not have a direct contact area between the moving part 22 and the frame 21. This helps to limit the areas subject to wear in the locking device 20 (by contact and / or relative movement between two elements of the locking device 20).

[0167] Advantageously, this 20 locking device has a relatively long lifespan.

[0168] In addition, this locking device 20 can present a torque resistance that can be adapted according to, for example, external parameters such as external temperature.

[0169] The locking device 20 is in particular shaped so as to be able to generate at least one magnetic field (via the magnet 41 and / or the coil 40) to modify in service the behavior of the fluid MR.

[0170] 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.

[0171] In particular, although in the illustrated embodiment each actuator is equipped with a locking device, only one or only part of the actuators may be equipped with a locking device.

[0172] Although here each locking device is associated with only one actuator, it can be foreseen that the same locking device may be associated with at least two actuators.

[0173] Although here the locking device is integrated into the associated actuator, the locking device may form a unitary module carried by the crown and / or the actuator housing (detachably or not). The locking device will then be arranged outside the actuator housing.

[0174] Multiple possibilities for the arrangement of the locking device relative to the motor can be envisaged and / or multiple possibilities for coupling between the moving part of the locking device and the actuation member.

[0175] This will allow the nut to be linked to the pusher (and not the screw as indicated here) so that it is the nut that is driven in rotation and not the screw.

[0176] For example, the locking device can be positioned at the end of the motor, i.e., in line with it, or laterally. For instance, the locking device can be positioned on the active side of the motor output shaft (i.e., the part that interacts with the drive) or on the passive side of the motor output shaft (opposite the active part). The motor output shaft can thus pass completely through a motor housing, allowing it to interact with the locking device on one side and with the drive on the other.

[0177] For example, the output shaft may be confused with the output shaft of the locking device or may form two separate parts.

[0178] For example, the motor output shaft may extend at least partially inside the locking device or may extend entirely outside the locking device.

[0179] For example, the moving part can cooperate indirectly with the electric motor. For instance, the two shafts can be connected together via at least one reduction gear. This gear may be the same as the one connecting the motor to the actuating element, or it may be a different gear, or it may share a common component with that other gear. Figure 7 illustrates a variant arrangement in which the moving part is coupled to the electric motor via the same reduction gear as the one connecting the motor to the actuating element.

[0180] For example, the moving part will be connected to the motor via the actuating element. For example, the screw of the actuating element and the shaft will be directly coupled together (possibly via a gear pair) or coupled together via at least one reduction gear. The X-axis can thus be parallel (coinciding or not) with the axis along which the screw extends longitudinally. For example, the locking device can be arranged next to the screw and / or at the end of the screw and on the opposite side from the pusher. For example, the output shaft of the moving part can be fitted with a gear capable of cooperating with the screw gear and / or with another gear mounted on the screw shaft. For example, the screw can be integrated with the output shaft of the locking device or form two separate parts.For example, the screw may extend at least partially inside the locking device or extend entirely outside the locking device.

[0181] The locking device may have a different shape than the one described.

[0182] For example, the frame can be shaped so as not to have an expansion chamber.

[0183] If the frame has an expansion chamber, the moving part can extend inside the expansion chamber to pass through the frame and thus be connected to an area of ​​the actuator.

[0184] The drum attachment portion may have a different shape than described. For example, the drum attachment portion may be shaped like a plate, or for example, like a disc with a circular cross-section. Similarly, the working portion may have only one wall capable of interacting with the MR fluid instead of two, or it may have more than two walls interacting with the MR fluid, for example, three or more.

[0185] The frame may be shaped differently from what has been described. For example, the frame may not include a sleeve.

[0186] Although the frame here comprises a single chamber containing a magnetorheological fluid, the number of chambers may vary, and the frame may thus have one or more chambers. The type of magnetorheological fluid, the geometry of the locking device, the material(s) of the locking device, the characteristics of the magnetic field(s) generated within the locking device, and the desired performance of the locking device can all be taken into account to determine the number of chambers. Although the inner and outer faces of at least one wall of the drum are in contact with the MR fluid, only one of the inner or outer faces of that wall may be in contact with the MR fluid.

[0187] The magnetic device may also differ from what has been indicated.

[0188] For example, according to a second embodiment illustrated in Figure 10, the device may not include a magnet (whether permanent, as in the first possibility, or programmable, as in the second). The magnetic device could then, for example, simply consist of a coil. In this case, when the coil is not energized, the MR fluid will be fluid, and the moving part will be able to move relative to the frame. Conversely, when the coil is energized, the magnetic field it generates will modify the viscosity of the MR fluid. The MR fluid will then be viscous, thus locking the moving part relative to the frame. It is therefore understandable that the coil must be activated following a locking command (for example, when engaging the parking brake) and deactivated following an unlocking command (for example, when disengaging the parking brake).This second method has the disadvantage of keeping the coil energized as long as the parking brake is engaged. However, it is simpler to construct and implement. Apart from what has been said in this paragraph, everything described for the first embodiment is also applicable to this second embodiment. In particular, with this second embodiment, it is also possible to implement a preferably closed control loop like the one described with reference to Figure 8.

[0189] The coil can be part of an electromagnet or can be used as such.

[0190] Although here the Y axis of rotation of the moving part in the frame of the locking device is parallel (optionally coincident) with the output shaft of the motor, the Y axis of rotation may be inclined with respect to the output shaft of the motor (for example due to the presence of at least one right-angle gear arranged between the output shaft of the motor and the moving part of the locking device).

[0191] Although here the motor shaft and the moving part of the locking device are directly linked in motion, the motor shaft and the moving part may be linked in motion through one or more reduction stages.

[0192] The coil's power supply can be started, increased, adjusted, stopped, and / or decreased to increase the viscosity of the MR fluid. Similarly, the coil's power supply can be started, increased, adjusted, stopped, and / or decreased to decrease the viscosity of the MR fluid.

[0193] Regardless of the specific configuration or embodiment, the locking device can be arranged to completely lock the moving part against the frame or to allow (if desired) controlled sliding between the moving part and the frame. The latter configuration can be used, for example, to prevent breakage of one or more parts of the electromechanical actuator. The number of chambers, the number of groove / wall pairs, the shape of the chambers, the shape of the grooves, and the shape of the walls can be adapted according to the desired level of sliding and / or locking.

[0194] Although in the first scenario the coil is not energized when the pushrod is retracted relative to the stack of discs, the coil can be energized even when the pushrod is retracted relative to the stack of discs. In this case, if a braking command is issued, it will be possible to directly energize the motor without waiting for the coil to be energized and therefore without waiting for the MR fluid to become fluid.

[0195] Although here we cut or activate the power supply to the coil, we can simply lower or raise the power supply to the coil to modify the behavior of the MR fluid (without totally disabling the coil).

[0196] Regardless of the possibility or embodiment considered, the magnetic device can be controlled in open loop or closed loop.

[0197] Although here the locking device is used to activate or deactivate the parking brake, the locking device can be used (in addition to or instead of) other functions.

Claims

DEMANDS 1. Electromechanical braking system comprising a stack of discs (15) and at least one electromechanical actuator, the actuator comprising at least one electric motor (17) and at least one actuating member connected to the motor (17) and capable of applying a force to the stack of discs (15), the actuator comprising at least one locking device (20) for the actuating member, characterized in that the locking device (20) comprises a frame (21), a movable part (22) relative to the frame, the movable part (22) being connected to the actuating member, the frame (21) defining at least one internal chamber within the locking device (20) in which at least a portion of the movable part is arranged, said chamber being at least partially filled with at least one magnetorheological fluid, the locking device (20) also comprising at least one magnetic device comprising at least one coil (40),an activation and / or deactivation of the coil (40) allowing modification of the behavior of the magnetorheological fluid.

2. System according to claim 1, wherein the locking device (20) is connected to the actuating member via at least one reduction assembly (14).

3. System according to claim 2, comprising a first reduction assembly arranged between the actuating member and the motor and a second reduction assembly arranged between the motor and the locking device.

4. System according to any one of the preceding claims, wherein the moving part (22) comprises at least one drum (25) and at least one output shaft (23) extending from the drum (25).

5. System according to claim 4, wherein the drum (25) comprises at least one wall extending into a groove of the frame (21) forming at least part of the chamber.

6. System according to any one of the preceding claims, wherein the magnetic device further comprises at least one magnet (41).

7. System according to claim 6, wherein the magnet (41) is a programmable magnet, and preferably surrounding the coil.

8. Aircraft landing gear comprising a system according to one of the preceding claims.

9. Aircraft comprising a landing gear according to claim 8.

10. A method for controlling a system according to any one of claims 1 to 7, to lock the moving part (22) vis-à-vis the frame (21) when the actuating member applies a force on the stack of discs (15), the method comprising at least the step of, following a locking command of the moving part (22) in the frame (21), supplying the coil or ceasing to supply the coil in order to modify the magnetic field generated by the magnetic device, vis-à-vis a magnetic field generated by the magnetic device before the locking command, and thus increase the viscosity of the magnetorheological fluid.

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