The invention relates to the field of braking aircraft wheels.
It is known to ensure braking of aircraft wheels by means of an electromagnetic braking actuator that moves a pusher so as to exert compressive force on a stack of disks comprising rotor disks constrained in rotation with the wheel and a stator disks constrained in rotation with the axle on which the wheel is rotatably mounted. The actuator generally comprises an electric motor for rotating an output shaft that is connected to a device for converting the movement in rotation of the output shaft into movement in translation of the pusher.
When the aircraft is parked, the compression force needs to be maintained on the stack of disks.
It is also known for the electromagnetic braking actuator to be fitted with a fail-safe parking brake that locks the shaft of the actuator motor when it is no longer powered and that unlocks the shaft as soon as the electric motor is powered. Such a parking brake needs to be powered for a considerable length of time while the electromagnetic actuator is in operation (i.e. during stages of landing, taxiing, and take-off). This increases the overall electricity consumption of the braking system and causes the coil of the parking brake to get hot. Furthermore, in the event of the parking brake failing, it remains engaged and applies the compression force continuously, which leads to premature wear of the stack of disks in the event of the aircraft taxiing with the brake locked, and can lead to the braking system being destroyed.
Improvements are described in Document FR-A-3 018 880.
An object of the invention is to further improve brake actuators, in particular to reduce electricity consumption and to improve reliability.
To this end, there is provided a motor sub-assembly for an electromechanical brake actuator of an aircraft wheel. The actuator comprises a casing, a shaft mounted in the casing to rotate about a longitudinal axis of the shaft, and an electric motor mounted in the casing and connected to a first end of the shaft in order to drive the shaft in rotation. The shaft has a second end arranged to be functionally connected to a movable element of a screw-and-nut assembly in order to exert a force on a stack of disks for braking the wheel. The shaft has a first set of teeth and the actuator has a shuttle mounted to slide relative to the casing and provided with a second set of teeth for co-operating with the first set of teeth. The actuator 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 holder device for holding the shuttle in its first position and a locking device for continuously preventing the shuttle from rotating relative to the casing.
In the meaning of the present application, a device for continuously preventing the shuttle from rotating means that the device is not declutchable.
An actuator motor sub-assembly is thus obtained that enables a brake pusher to be held stationary without requiring electrical energy to remain in this state. Such an actuator motor sub-assembly can be installed in lubricated surroundings, unlike friction brake devices, which means there is no need to provide sealed compartments in the actuator, thereby improving the costs of manufacturing such an actuator.
A device that is particularly inexpensive is obtained when the shuttle is mounted on the shaft to provide a sliding and pivoting connection relative to the shaft. Specifically, such a connection is simpler and less expensive to make than is a slideway connection.
The weight of the equipment is reduced when the selector mechanism comprises a coil.
The actuator motor sub-assembly is easier to manufacture when the locking device for continuously preventing the shuttle from rotating relative to the casing comprises at least one guide secured to the casing and on which the shuttle is guided to slide along a direction substantially parallel to the longitudinal axis.
The lifetime of the actuator motor sub-assembly is improved when the shuttle comprises a first portion made of non-ferromagnetic material and a second portion made of ferromagnetic material.
Advantageously, the actuator motor sub-assembly further comprises a device for holding the shuttle in its second position.
Advantageously, the device for holding the shuttle in its first position comprises a permanent magnet and/or the device for holding the shuttle in its second position comprises a permanent magnet.
A torque-limiting function is obtained when the first set of teeth and/or the second set of teeth includes a face lying in a first plane intersecting the longitudinal axis, the first angle between the first plane and the longitudinal axis lying in the range 5° to 85°. It should be recalled that, in conventional manner, the angle between the first plane and the longitudinal axis corresponds to the (unsigned) angle that the longitudinal axis makes with its orthogonal projection onto the first plane.
Also advantageously, the electric motor is located in the casing between the shuttle and the output of the actuator.
The invention also provides an actuator including a motor sub-assembly of the above-mentioned type, a braking system including such an actuator, and an aircraft including such a braking system.
Other characteristics and advantages of the invention appear on reading the following description of particular, nonlimiting embodiments of the invention.
Reference is made to the accompanying figures, in which:
With reference to
The braking system includes an electromagnetic brake actuator, given overall reference 1, that is arranged to exert a compression force on a stack of disks 9 comprising rotor disks constrained in rotation with the wheel and stator disks constrained in rotation with the axle (not shown) on which the wheel is mounted to rotate.
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 that is connected to the brake-actuator sub-assembly 70 by a gear train 3. The brake-actuator sub-assembly 70 comprises a nut 4 that is mounted to be stationary in translation and free to move in rotation under rotary drive from the gear train 3. The nut 4 has a thread 5. A pusher 6 is constrained to move in translation with a ball-screw 7 that co-operates with the thread 5. The screw 7 is fitted with anti-rotation means (specifically a central guide 8) so that rotation of the nut 4 drives movement in translation of the screw 7 and thus of the pusher 6. The pusher 6 thus acts on command to exert a compression force on the stack of disks 9. This arrangement is itself known and it is not described in greater detail herein.
As can be seen in
A shuttle 30 is mounted on the shaft 15 to provide a sliding and pivoting connection relative to the shaft 15 and to provide a slideway connection relative to the casing 11 (i.e. a sliding-only connection). At its first end 31, the shuttle 30 is provided with a second set of teeth 32 suitable for co-operating with the first set of teeth 18. As can be seen in
The shuttle 30 can adopt two extreme positions, namely:
Thus, when the shuttle 30 is in its first position, it is constrained in rotation with the shaft 15 by the first and second sets of teeth 18 and 32. Since the shuttle is continuously locked against rotating relative to the casing 11, the shaft 15 is locked against rotating relative to the casing 11. When the shuttle 30 is in its second position, the shaft 15 is free to rotate about the longitudinal axis Oy relative to the casing 11. 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 manner, in the absence of the first and second coils 38 and 39 being powered, the shuttle 30 is held in its second position by the permanent magnet 40 exerting a second magnetic force Fm2.
In operation, when the pilot of the aircraft issues a braking command, the electronic braking control unit powers the upper and lower coils 38 and 39 so that they exert a second magnetic force Fb1 on the ring 34.1 that is sufficient to overcome the first magnetic force Fm1 and move the shuttle 30 towards its second position (
This procures a brake actuator with reduced electricity consumption.
When the stack of disks 9 applies an opposing force on the pusher 6 that is greater than the braking force, e.g. as a result of phenomena associated with thermal expansion/contraction of the brake after braking, this opposing force greater than the braking force gives rise to an opposing torque being applied to the shaft 15 via the drive train connecting together the pusher 6 and the shaft 15 (
In a second embodiment, shown in
Naturally, the invention is not limited to the embodiments described, but covers any variant coming within the ambit of the invention as defined by the claims.
In particular:
Number | Date | Country | Kind |
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20 13009 | Dec 2020 | FR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2021/083830 | 12/1/2021 | WO |