Actuator with integrated parking brake

Abstract

The invention relates to a motor sub-assembly of an electromechanical actuator for braking the wheels of an aircraft, comprising a housing, a shaft mounted in the housing to pivot about a longitudinal axis of the shaft, a shuttle comprising a second set of teeth mounted to slide with respect to the housing and arranged to engage the first set of teeth, the actuator further comprising a selection mechanism for selectively moving the shuttle in a first position in which the first set of teeth engages the second set of teeth and in a second position in which the first set of teeth is disengaged from the second set of teeth, the actuator comprising means for retaining the shuttle in its first position and means for permanently preventing the rotation of the shuttle with respect to the housing.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of braking aircraft wheels. BACKGROUND

[0002] It is known to ensure the braking of an aircraft wheel by means of an electromagnetic braking actuator which moves a pusher in order to exert a compression force on a wheel disc stack comprising a rotor disc constrained to rotate with the wheel and a stator disc constrained to rotate with a wheel axle on which the wheel is rotatably mounted. The actuator generally comprises an electric motor for rotating an output shaft which is connected to a device for converting the rotational movement of the output shaft into a translational movement of the pusher.

[0003] The compression force needs to be maintained on the wheel disc stack when the aircraft is parked.

[0004] It is also known for the electromagnetic braking actuator to be fitted with a failsafe parking brake which locks the shaft of the actuator motor when the latter is no longer powered and which unlocks this shaft as soon as the motor is powered. This parking brake needs to be powered for quite a long time when the electromagnetic actuator is operating, i.e. during the phases of landing, taxiing and takeoff. This increases the overall power consumption of the braking system and causes the coil of the parking brake to heat up. Furthermore, in the event of a failure of the parking brake, it remains engaged and continues to exert a compression force, which leads to premature wear of the wheel disc stack in the event of a plane taxiing and the brake being locked, and can cause the braking system to be damaged.

[0005] Improvements are described in document FR A 3 018 880. SUMMARY

[0006] The aim of the present invention is to further improve the braking actuator, in particular to reduce the power consumption and to increase the reliability.

[0007] To this end, a motor sub-assembly for an electromechanical braking actuator of an aircraft wheel is provided. The motor sub-assembly comprises a housing, a shaft mounted in the housing for rotation about a longitudinal axis of the shaft, and an electric motor mounted within the housing and connected to a first end of the shaft to drive rotation of the shaft. The shaft has a second end arranged to functionally connect to a movable element of a screw-nut assembly in order to exert a force on a wheel disc stack for braking the wheel. The shaft has a first set of teeth and the actuator has a shuttle mounted to slide with respect to the housing and provided with a second set of teeth for cooperating with the first set of teeth. The motor sub-assembly further comprises a selector mechanism for selectively moving the shuttle between a first position in which the first set of teeth is engaged with the second set of teeth and a second position in which the first set of teeth is disengaged from the second set of teeth. The actuator further comprises a retainer device for retaining the shuttle in its first position and a locking device for continuously preventing rotation of the shuttle with respect to the housing.

[0008] In the sense of the present application, the device for continuously preventing rotation of the shuttle means that the device is inseparable.

[0009] There is thus obtained an actuator motor sub-assembly which enables the brake pusher to remain stationary without requiring electrical energy to remain in this state. Unlike a friction brake device, this actuator motor sub-assembly can be installed in a lubricated environment, which means that it is not necessary to provide a sealed compartment in the actuator, thereby improving the cost of manufacturing such an actuator.

[0010] A particularly inexpensive device is obtained when the shuttle is mounted on the shaft to provide a sliding and pivoting connection with respect to the shaft. In particular, such a connection is simpler and less costly than a sliding track connection.

[0011] The weight of the device is reduced when the selector mechanism comprises a coil.

[0012] The actuator motor sub-assembly is easier to manufacture when the locking device for continuously preventing rotation of the shuttle with respect to the housing comprises at least one guide fixed to the housing and on which the shuttle is guided to slide in a direction substantially parallel to the longitudinal axis.

[0013] The lifetime of the actuator motor sub-assembly is improved when the shuttle comprises a first portion made of a non-ferromagnetic material and a second portion made of a ferromagnetic material.

[0014] Advantageously, the actuator motor sub-assembly also comprises a device for retaining the shuttle in its second position.

[0015] Advantageously, the device for retaining the shuttle in its first position comprises a permanent magnet and / or the device for retaining the shuttle in its second position comprises a permanent magnet.

[0016] A torque limitation function is obtained when the first set of teeth and / or the second set of teeth comprise a face lying in a first plane intersecting the longitudinal axis, the first angle between the first plane and the longitudinal axis being in the range 5° to 85°. It should be remembered that, in a conventional manner, the angle between the first plane and the longitudinal axis corresponds to the (unsigned) angle formed by the longitudinal axis and its orthogonal projection on the first plane.

[0017] It is also advantageous for the electric motor to be located in the housing between the shuttle and the output of the actuator.

[0018] The application also provides an actuator comprising a motor sub-assembly of the type described above, a braking system comprising such an actuator and an aircraft comprising such a braking system.

[0019] Other features and advantages of the present application will appear upon reading the following description of a concrete, non-limitative embodiment thereof, given as an example with reference to the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] With reference to the drawings, in which:

[0021] - Figure 1 is a schematic view of a braking system of the present application;

[0022] - Figure 2 is a schematic view, in cross-section, of an actuator in a first state in a first embodiment of the present application;

[0023] - Figure 3 is a schematic view, in cross-section, of the actuator on a plane III-III; Figure 2 -

[0024] is a schematic view, in cross-section, of the actuator in a second state; Figure 4 Figure 2 - is a schematic view, in cross-section, of the actuator in an intermediate third state; and

[0025] Figure 5 Figure 2

[0026] - Figure 6 is a schematic view, in cross-section, of an actuator in a first state in a second embodiment of the present application. DETAILED DESCRIPTION

[0027] With reference to the drawings, in which: Figures 1 to 6 The present application relates to a system for braking a wheel 10 of an aircraft (not shown).

[0028] The braking system comprises an electromagnetic braking actuator, generally designated 1, arranged to exert a compression force on a disc stack 9 comprising rotor discs constrained to rotate with the wheel and stator discs constrained to rotate with a wheel shaft (not shown) on which the wheel is mounted to rotate.

[0029] ​​​The electromagnetic actuator comprises a motor sub-assembly 60 and a brake actuator sub-assembly 70. The motor sub-assembly 60 comprises an electric motor 12 having an output shaft 2 connected to the brake actuator sub-assembly 70 by a gear train 3. The brake actuator sub-assembly 70 comprises a nut 4 mounted for non-translational but free rotational movement under rotational drive from the gear train 3. The nut 4 has a thread 5. A pusher 6 is constrained for translational movement with a ball screw 7 which cooperates with the thread 5. The screw 7 is fitted with anti-rotation means, in particular a central guide 8, such that rotational drive of the nut 4 drives translational movement of the screw 7, and thus of the pusher 6. The pusher 6 is thus commanded to exert a compression force on a stack 9 of brake discs. This arrangement is known per se and will not be described in more detail here.

[0030] As shown in Figure 2 , the motor sub-assembly 60 comprises a housing 11 which encloses the electric motor 12 connected to an electronic brake control unit (not shown) having electronic circuitry controlling an electronic power supply circuit for powering the motor 12. The motor 12 comprises a stator 13 fastened to the housing 11, and a rotor 14 fixed to a first end 15.1 of a shaft 15 mounted in the housing 11 for rotation about a longitudinal axis Oy by means of a first bearing 16 and a second bearing 17. The shaft 15 has a second end 15.2 projecting outside the housing 11 and having teeth for constituting the output 2 of the motor sub-assembly 60. The shaft 15 is provided with a first set of teeth 18 having three teeth 19. The teeth 19 are triangular, being defined by face portions 20 and 21 lying in respective planes which do not contain the longitudinal axis Oy (in other words, intersecting the axis Oy) and are not perpendicular to said axis.

[0031] The shuttle 30 is mounted on the shaft 15 to provide a sliding and pivotal connection with respect to the shaft 15, and a sliding (i.e. only sliding) connection with respect to the housing 11. At a first end 31 of the shuttle 30, the shuttle 30 is provided with a second set of teeth 32 adapted to cooperate with the first set of teeth 18. As shown in Figure 2 , the shuttle 30 is located in the housing 11 between the motor 12 and the outlet 2. As shown in Figure 3As shown, the shuttle 30 has a cylindrical tubular central first portion 33 made of bronze, which has a collar 34 projecting radially therefrom, also made of bronze. The central first portion 33 is smooth and extends around the smooth portion of the shaft 15. A ring 34.1 of ferromagnetic material, in particular ferrite, is located at the periphery of the collar 34. The collar 34 comprises a hole 35 which receives a steel guide 36 fixed to the housing 11 and on which the shuttle 30 is guided to slide in a direction substantially parallel to the longitudinal axis Oy. The guide 36 and the hole 35 constitute a locking device which continuously prevents the shuttle 30 from rotating relative to the housing 11. The housing 11 defines a housing 37 which receives a first coil 38 located alongside the motor 12 and a second coil 39 located alongside the output 2, the two coils being spaced apart from each other by a permanent magnet 40. The permanent magnet 40 is held in place by an annular support 41 made of ferromagnetic material and having a first flange 42 and a second flange 43. The first flange 42 faces a first outer side 38.1 of the first coil 38. The second flange 43 faces a second outer side 39.2 of the second coil 39. The first coil 38 and the second coil 39 are electrically connected to an electronic brake control unit. The housing 37 is closed by a cover 44 made of ferromagnetic material and having an opening 45 for the passage of the shaft 15.

[0032] The shuttle 30 can adopt two extreme positions, namely:

[0033] - a first position, as shown in Figure 2, in which the collar 34 is closer to the first coil 30, the first set of teeth 18 being engaged with the second set of teeth 32; and Figure 2

[0034] - a second position, as shown in Figure 3, in which the collar 34 is closer to the second coil 39, the first set of teeth 18 being disengaged from the second set of teeth 32. Figure 4

[0035] Thus, when the shuttle 30 is in its first position, it is constrained to rotate with the shaft 15 by the first set of teeth 18 and the second set of teeth 32. Since the shuttle is continuously locked against rotation relative to the housing 11, the shaft 15 is locked against rotation relative to the housing 11. When the shuttle 30 is in its second position, the shaft 15 is free to rotate relative to the housing 11 about the longitudinal axis Oy. The permanent magnet 40 and the ferrite ring 34.1 have respective polarities and dimensions such that the shuttle 30 is held in its first position by the permanent magnet 40 exerting a first magnetic force Fm1. In the same way, in the absence of electrical supply to the first coil 38 and to the second coil 39, the shuttle 30 is held in its second position by the permanent magnet 40 exerting a second magnetic force Fm2.

[0036] ​​During operation, when the aircraft pilot issues a braking command, the electronic braking control unit supplies power to the upper coil 38 and the lower coil 39, causing them to apply a first magnetic force Fb1 to the ring 34.1. This magnetic force Fb1 is sufficient to overcome the first magnetic force Fm1 and move the shuttle 30 to its second position. Figure 2 When the electronic brake control unit stops supplying power to the upper coil 38 and the lower coil 39, the shuttle 30 remains in its second position under the action of the permanent magnet 40. Figure 4 The field lines of the permanent magnet 40 pass through the ring 34.1, the housing 11, and the second flange 43 of the support 41 to form a loop (forming a circuit). The electronic braking control unit can then energize the motor 12 to apply a compressive force to the wheel stack 9 in a conventional manner, thereby stopping the aircraft during gliding. Once the aircraft is docked in its parking position, the electronic braking control unit controls the motor 12 to apply a compressive force to hold the aircraft in place. The electronic braking control unit then powers the upper coil 38 and the lower coil 39, causing them to apply a second magnetic force Fb2 to the ring 34.1, sufficient to return the shuttle 30 to its first position. Figure 4 When the electronic brake control unit stops supplying power to the upper coil 38 and the lower coil 39, the shuttle 30 remains in its second position under the action of the permanent magnet 40. Figure 2 The field lines of the permanent magnet 40 pass through the ring 34.1, the cover 44, and the second flange 42 of the support member 41 to form a loop (forming a circuit). In this first position, the shaft 15 is locked to prevent rotation, and the force applied by the pusher 6 is maintained. After an appropriate time delay, the electronic brake control unit stops supplying power to the motor 12, and without consuming energy, the motor subassembly 60 is used to apply a compressive force (i.e., parking force) to keep the aircraft in place.

[0037] This results in a braking actuator with reduced power consumption.

[0038] When the wheel stack 9 (e.g., due to phenomena related to the thermal expansion / contraction of the brake after braking) applies a force greater than the braking force to the pusher 6, this force generates a counter-torque via the transmission system connecting the pusher 6 and the shaft 15. Figure 5 The opposing torque is applied to shaft 15. When the opposing torque exceeds a predetermined threshold, the force applied by the first set of teeth 18 to the second set of teeth 32 is sufficient to overcome the first magnetic force Fm1, thereby pushing the shuttle 30 back. Figure 5 This allows shaft 15 to rotate relative to housing 11, thus acting as a limiter for the torque applied to motor subassembly 60. The opposing torque gradually decreases as shaft 15 rotates. When it falls below a threshold, the opposing torque is no longer sufficient to overcome the first magnetic force Fm1, and shuttle 30 returns to its first position. This re-engagement corresponds to the aircraft applying its parking brake.

[0039] In a second embodiment, as shown in Figure 6 The motor 12 is located in the housing 11 between the shuttle 30 and the output 2 of the actuator 1.

[0040] Of course, the application is not limited to the described embodiments, but covers any variants falling within the scope of the application as defined by the claims.

[0041] In particular:

[0042] - although, as described above, the first and second sets of teeth comprise three triangular teeth, the application is equally applicable to other types of tooth sets, such as tooth sets having one, two, four or more teeth. The tooth sets can have some other profile, for example helical, saw-toothed or any other profile, having at least one face lying in a plane intersecting the longitudinal axis, wherein the first angle between the first plane and the longitudinal axis is in the range 5° to 85°;

[0043] - although, as described above, the shuttle comprises a central portion made of bronze and a ring of ferromagnetic material, the application is equally applicable to other types of material for the shuttle, for example a shuttle made entirely of ferromagnetic material, or a shuttle in which the central portion is made of non-magnetic stainless steel;

[0044] - although, as described above, the actuator has two coils, the application is equally applicable to other types of selector mechanism for causing the shuttle to travel from its first position to its second position, for example a single coil, more than two coils, a fork mechanically acting on the shuttle, or a pusher;

[0045] - although, as described above, the actuator comprises a permanent magnet acting on the ferromagnetic portion of the shuttle, the application is equally applicable to other types of device for retaining the shuttle in its first position, for example a spring or a stack of spring washers;

[0046] - although, as described above, the actuator comprises a guide fixed to the housing and on which the shuttle slides, the application is equally applicable to other types of locking device for continuously (continuously) preventing the shuttle from rotating relative to the housing, for example a shuttle having a groove mating with a complementary groove of the housing;

[0047] - although, as described above, the actuator causes the nut to rotate, the application is equally applicable to an actuator causing the other element of the lead screw and nut assembly (for example the lead screw) to rotate;

[0048] - although, as mentioned above, the actuator comprises a medium made of ferromagnetic material, the application is equally applicable to an actuator that does not have such a medium, the arrangement of the coil and the permanent magnet alone being sufficient to retain the collar in two stable states, namely a first state in which the collar is in its first position and a second state in which the collar is in its second position; and

[0049] - although, as mentioned above, the guide is made of steel, the application is equally applicable to a guide made of other materials, for example, bronze or other nickel-copper-tin alloys.

Claims

1. A motor sub-assembly for an electromechanical brake actuator of an aircraft wheel, the motor sub-assembly comprising a housing, a shaft mounted in the housing for rotation about a longitudinal axis of the shaft, and an electric motor mounted in the housing and connected to a first end of the shaft to drive rotation thereof, the shaft having a second end arranged to functionally connect to a movable element of a screw and nut assembly to apply a force to a disc stack for braking the wheel, characterized in that, The shaft has a first set of teeth, the motor sub-assembly has a shuttle mounted for sliding movement relative to the housing and provided with a second set of teeth for cooperation with the first set of teeth, wherein the motor sub-assembly comprises a selector mechanism to selectively move the shuttle between a first position in which the first set of teeth is engaged with the second set of teeth and a second position in which the first set of teeth is disengaged from the second set of teeth, the motor sub-assembly comprises a retaining device to retain the shuttle in its first position and a locking device to continuously prevent rotation of the shuttle relative to the housing.

2. The actuator motor subassembly of claim 1, wherein, The shuttle is mounted on the shaft to provide a sliding and pivotal connection relative to the shaft.

3. The actuator motor subassembly of claim 2, wherein, The sliding and pivotal connection comprises a central first portion extending around a smooth portion of the shaft.

4. The actuator motor subassembly of claim 1 or 2, wherein, The shuttle is mounted to provide a sliding connection relative to the housing.

5. The actuator motor subassembly of any of the preceding claims 1 to 3, characterized in that, The selector mechanism comprises a coil.

6. The actuator motor subassembly of any of the preceding claims 1 to 3, characterized in that The locking device to continuously prevent rotation of the shuttle relative to the housing comprises at least one guide fixed to the housing, the shuttle being guided over the at least one guide to slide in a direction substantially parallel to the longitudinal axis.

7. The actuator motor subassembly of any of the preceding claims 1 to 3, characterized in that The shuttle comprises a first portion made of a non-ferromagnetic material and a second portion made of a ferromagnetic material.

8. The actuator motor subassembly of any of the preceding claims 1 to 3, characterized in that The shuttle is located in the housing between the electric motor and the output of the actuator.

9. The actuator motor subassembly of any of the preceding claims 1 to 3, characterized in that There is further included a retaining device to retain the shuttle in its second position.

10. The actuator motor subassembly of any of the preceding claims 1 to 3, characterized in that The retaining device to retain the shuttle in its first position comprises a permanent magnet.

11. The actuator motor subassembly of claim 9, wherein, The retaining device to retain the shuttle in its second position comprises a permanent magnet.

12. The actuator motor subassembly of any of the preceding claims 1 to 3, characterized in that The first set of teeth and / or the second set of teeth comprise a face portion located in a first plane intersecting the longitudinal axis, a first angle between the first plane and the longitudinal axis being in the range of 5° to 85°.

13. The actuator motor subassembly of any of the preceding claims 1 to 3, characterized in that The electric motor is located in the housing between the shuttle and the output of the actuator.

14. A brake actuator comprising a motor sub-assembly according to any one of the preceding claims.

15. A brake system for an aircraft wheel, the brake system comprising a disc stack having a rotor disc constrained to rotate with the wheel, a stator disc constrained to rotate with a wheel axle on which the wheel is rotatably mounted, and an actuator according to claim 14 for applying a compression force on the disc stack.

16. An aircraft comprising at least one wheel provided with a brake system according to claim 15.

Images