Aircraft wheel braking device

Abstract

The invention relates to an aircraft wheel (1) braking device (10), comprising: - a torque tube (13, 13') extending along a longitudinal axis; - a stack of brake discs (11) including a last stator disc; - at least one actuator (18) comprising a piston translatably mounted between a first end position in which the piston is spaced apart from the stack of discs and a second end position, in order to exert a pressing force on the first stator disc; and - at least one stud (14) arranged between a second end of the torque tube and the last stator disc in order to take up and transfer the pressing force to the torque tube. The last stator disc and the torque tube are shaped so as to define therebetween a minimum clearance which is less than the distance separating the piston from its second end position when the piston exerts the pressing force.

Description

[0001]BRAKING DEVICE FOR AN AIRCRAFT WHEEL The invention relates to the field of aircraft wheel braking. BACKGROUND OF THE INVENTION An aircraft wheel is traditionally rotatably mounted on an axle carried by a lower end of a landing gear leg. The aircraft wheel may be provided with a braking device for slowing and immobilizing the aircraft when it is on the ground. The braking device generally comprises a stack of discs comprising stator discs and rotor discs which are stacked alternately on a torque tube fixed to the axle. The stator discs are fixed in rotation relative to the axle and comprise a first stator disc and a last stator disc between which the rotor discs and the other stator discs extend. The rotor discs are linked in rotation to the wheel. The braking device also comprises: − a hydraulic crown which is fixed to a first end of the torque tube andwhich comprises actuators provided with pistons arranged opposite the first stator disc to selectively exert a pressing force on the stack of discs; and − pads arranged between the last stator disc and a second end of the torque tube to take up and transfer the pressing force to the torque tube. The heat release resulting from friction of the discs can be significant (particularly during landing of the aircraft where the energy to be dissipated is at a maximum due to the mass and high speed of the aircraft) and cause axial creep of the pads, and therefore a displacement of the stack of discs which can cause the last stator disc to be in abutment against the torque tube. The stroke of the pistons can then prove insufficient to continue to exert a pressing force on the stack of discs, particularly when the discs are worn. It has been considered to use actuators having a greater stroke. Such a solution provesnevertheless heavier and more cumbersome, and difficult to implement in an already defined and very constrained environment. It has also been considered to reduce the maximum permissible wear of the discs. However, this leads to more frequent disc changes and therefore a significant cost for the company operating the aircraft. OBJECT OF THE INVENTION The invention therefore aims to propose an aircraft wheel braking device making it possible to at least partially overcome the aforementioned problems. SUMMARY OF THE INVENTION In order to achieve this object, the invention proposes a braking device for an aircraft wheel comprising: − a torque tube extending along a longitudinal axis; − a stack of brake discs comprising stator discs and rotor discs stacked alternately on the torque tube, the stator discs comprising a first stator disc and a last stator disc between which are arranged intermediate stator discs inalternation with the rotor discs; − at least one actuator which is fixed to a first end of the torque tube and which comprises a piston mounted movable in translation along an axis parallel to the longitudinal axis, between a first extreme position in which the piston is distant from the stack of discs and a second extreme position, to exert a pressing force on the first stator disc; and − at least one stud arranged between a second end of the torque tube and the last stator disc to take up and transfer the pressing force to the torque tube. According to the invention, the last stator disc and the torque tube are shaped to define between them, along the longitudinal axis, a minimum clearance which, for a given maximum wear of the discs, is less than the distance separating the piston from its second extreme position when said piston exerts the pressing force. Thus, in the event of creep of the stud tending to bring the last stator disc into abutment against thesecond end of the torque tube (in particular during emergency braking), the stroke of the piston remains sufficient for said piston to continue to exert the pressing force. It will be noted that such an adaptation of the last stator disc and / or the torque tube does not impact the other components of the braking device. According to a particular characteristic, the last stator disc comprises at least one boss extending projecting from a rear face of the last stator disc, the boss defining, with the torque tube, the minimum clearance. In particular, the boss comprises a main face extending in a plane orthogonal to the longitudinal axis, the main face defining, with the torque tube, the minimum clearance. In particular, the braking device comprises a plurality of studs equally distributed around the longitudinal axis, the last stator disc comprising a plurality of bosses each extending between two neighboring studs.In particular, the bosses are in the shape of an arc of a circle and are inscribed in a circle whose center belongs to the longitudinal axis. According to another particular characteristic, the last stator disc comprises a rear face defining with the torque tube, the minimum clearance. According to another particular characteristic, the second end of the torque tube comprises at least one boss defining, with the last stator disc, the minimum clearance. The invention also relates to an aircraft wheel equipped with such a braking device. The invention also relates to an aircraft landing gear comprising at least one such wheel. The invention further relates to an aircraft comprising at least one such landing gear. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood in the light of the following description, which is purely illustrative and non-limiting, and must be read in conjunction with the appended drawings, among which: [Fig. 1] Figure 1 is a representationsimplified view of an aircraft comprising wheels equipped with a braking device according to a first embodiment of the invention; [Fig.2] Figure 2 is an axial sectional view of one of the braked wheels of the aircraft illustrated in Figure 1; [Fig.3A] Figure 3A is a perspective view of the last stator disc of the braking device equipping the wheel illustrated in Figure 2; [Fig.3B] Figure 3B is an axial sectional view of the torque tube and the last stator disc illustrated in Figure 3A; [Fig.3C] Figure 3C is a perspective view of a variant of the last stator disc illustrated in Figure 3A; [Fig.4A] Figure 4A is an axial sectional view of the last stator disc and the torque tube of a braking device according to a second embodiment of the invention; [Fig.4B] Figure 4B is an axial sectional view of a first variant of the last stator disc illustrated in Figure 4A; [Fig.4C] Figure 4C is an axial sectional view of a second variantof the last stator disc illustrated in Figure 4A; [Fig.5] Figure 5 is an axial sectional view of the last stator disc and the torque tube of a braking device according to a third embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION An aircraft A comprises, as illustrated in Figure 1, two main landing gears P each comprising a leg J ​​having a first end articulated on a structure S of the aircraft A and, opposite, a second end carrying wheels 1 rotating about an axis X on a tubular axle E. The leg J ​​is movable between a retracted position (not shown) and a deployed position illustrated here. The wheels 1 are said to be "braked", that is to say equipped with a braking device 10 intended to selectively slow down and stop the aircraft A when it is on the ground. The following description relates to one of the braked wheels 1, the braked wheels 1 of the aircraft A being here identical but can also bedifferent. With reference to Figure 2, the wheel 1 comprises two half-wheels 1a, 1b which each comprise an annular rim 2a, 2b connected by a web 3a, 3b to a half-hub 4a, 4b pivotally received on the axle E by means of bearings 5a, 5b. The half-wheel 1a comprises a housing formed on an edge of the rim 2a and in which a seal 6 is arranged so that it is elastically compressed between the half-wheels 1a, 1b once they are assembled. The half-wheels 1a, 1b are brought together in a direction parallel to the axis X of rotation of the wheel 1 and comprise centering surfaces to ensure the correct relative positioning of the half-wheels 1a, 1b. The half-wheels 1a, 1b are held in position by assembly bolts 7 arranged in holes drilled opposite each other in the webs 3a, 3b. The bolts 7 are screwed and tightened to assemble the half-wheels 1a, 1b after mounting a tire (not shown) on the rims 2a, 2b between sidewalls ofthese. In this position, the seal 6 is elastically compressed between the half-wheels 1a, 1b and thus prevents the gas contained in a volume delimited by the tire and the half-wheels 1a, 1b from escaping to the outside of the wheel 1. In a manner known per se, the braking device 10 comprises carbon brake discs 11, including stator discs 11.1, 11.2, 11.3, 11.4, 11.5 and rotor discs 12.1, 12.2, 12.3, 12.4, which are stacked alternately against each other on a torque tube 13 fixed to a hand E1 of the axle E. The torque tube 13 and the stack of discs 11 extend inside the half-wheel 1a in an annular space delimited by an inner surface of the rim 2a, the veil 3a and an outer surface of the half-hub 4a extending opposite the inner surface of the rim 2a. The stator discs 11.1, 11.2, 11.3, 11.4, 11.5 comprise in particular a first stator disc 11.1 and a last stator disc 11.5between which extend the rotor discs 12.1, 12.2, 12.3, 12.4 and the other stator discs 11.2, 11.3, 11.4 hereinafter called “intermediate stator discs”. The first stator disc 11.1 and the intermediate stator discs 11.2, 11.3, 11.4 comprise axial peripheral notches each receiving a section of a tenon (not shown) fixed on an outer surface of the torque tube 13. The tenons extend along an axis parallel to the axis X of rotation of the wheel 1 and ensure a rotational coupling of said first stator disc 11.1 and said intermediate stator discs 11.2, 11.3, 11.4 with the torque tube 13 around said axis X. The last stator disc 11.5 comprises a friction front face 11a which faces the rotor disc 12.4, and a rear face 11b, opposite the front face 11a, which faces a first end of the torque tube 13 close to the web 3a. The front face 11a and the rear face 11b each extend in a planesubstantially orthogonal to the X axis and define a thickness e of the stator disc 11.5. With reference to Figure 3A, the rear face 11b of the last stator disc 11.5 comprises a plurality of cylindrical recesses 11c which are equally distributed around the X axis and in which studs 14, also called “pucks”, secured to the first end of the torque tube 13 are received. The last stator disc 11.5 also comprises holes 11d passing through it, each hole 11d comprising a conical shoulder and opening into one of the recesses 11c of the rear face 11b. A rivet 15 extending into each hole 11d makes it possible to fix each stud 14 to the last stator disc 11.5. The studs 14 are identical and comprise a tubular end 14a extending along an axis parallel to the axis X, projecting from the rear face 11b of the last stator disc 11.5. The end 14a of each of the studs 14 is received in a bore 13a formed in the first end of the tube oftorsion 13, so that said studs 14 ensure a rotational coupling of the last stator disc 11.5 with the torsion tube 13 around the axis X. Furthermore, the end 14a of the studs 14 comprises a shoulder 14b bearing against a peripheral edge of the bore so as to take up and transfer, as will be seen later, press forces applied to the stack of discs 11 to the torsion tube 13. The rotor discs 12.1, 12.2, 12.3, 12.4 comprise axial peripheral notches each receiving a section of a bar (not shown) fixed on the inner surface of the rim 2a. The bars extend along an axis parallel to the axis X of rotation of the wheel 1 and ensure a rotational coupling of the rotor discs 12.1, 12.2, 12.3, 12.4 with the rim 2a around said axis X. The braking device 10 further comprises a hydraulic crown 16 fixed to a second end of the torque tube 13 by means of screws 17. The crown 16 comprises aplurality of cavities 16a distributed equally around the axis X of rotation of the wheel 1 and connected to each other by channels 16b. Each of the cavities 16a receives an actuator 18 selectively exerting, along an axis parallel to the axis X, a pressing force on the stack of discs 11 via a pressurized hydraulic fluid circulating inside the crown 16 through the channels 16b. Each actuator 18 comprises a generally cylindrical sleeve 18.1 which is received in a sealed manner in the cavity 16a of the crown 16, and a piston 18.2 which is mounted in the sleeve 18.1 to slide along an axis parallel to the axis X of rotation of the wheel 1, between a first extreme position (illustrated in FIG. 2) in which the piston 18.2 is retracted into the sleeve 18.1, and a second extreme position (not shown) in which said piston 18.2 is removed from said sleeve 18.1. The first extreme position and the second extreme position define the stroke of the piston 18.2.One end of the piston 18.2 receives a pad 18.3 arranged to exert the pressing force on the first stator disc 11.1 of the stack of discs 11. The equitable distribution of the actuators 18 around the X axis makes it possible to equitably distribute the pressing forces exerted by the pistons 18.2 on the first stator disc 11.1 (via the pads 18.3). The application of the pressing forces on the first stator disc 11.1 forces all of the discs 11 to rub against each other so that part of the kinetic energy of the aircraft A is dissipated as heat. The friction of the discs 11 causes wear of the different friction faces of the stator discs 11.1, 11.2, 11.3, 11.4, 11.5 and the rotor discs 12.1, 12.2, 12.3, 12.4, and therefore a reduction in their thickness. According to a first embodiment of the braking device 10, the last stator disc 11.5 comprises, between each of the recesses 11c, a boss 11e in an arc of a circle extending in projection from the facerear 11b of said last stator disc 11.5 (figures 3A and 3B). The bosses 11e extend from a recess 11c to a neighboring recess 11c and are here inscribed in a circle whose center belongs substantially to the axis X. Each of the bosses 11e comprises a main face 11f which extends in a plane parallel to the rear face 11b and which is arranged to come into abutment against an end face 13b of the torque tube 13 in the event of axial creep of the studs 14, in particular during emergency braking exerted by the actuators 18. The bosses 11e thus form pads or skates making it possible to take up and transfer the press force to the torque tube 13 in the event of failure of the studs 14. The main faces 11f of the bosses 11e and the end face 13b of the torque tube 13 are arranged to define a minimum clearance J, along the axis X, between the last stator disc 11.5 and torque tube 13. The minimum clearance J is lower, for a given maximum wear of the discs11, at the distance separating the pistons 18.2 from the actuators 18 from their second extreme position when said pistons 18.2 exert a pressing force on the first stator disc 11.1. Thus, in the event of axial creep of the studs 14 tending to move the stack of discs and bring the last stator disc 11.5 into abutment against the end of the torque tube 13, the pistons 18.2 can continue to exert a pressing force on the stack of discs 11. Figure 3C illustrates a variant of the last stator disc 11.5 illustrated in Figure 3A, in which the bosses 11e each extend between two neighboring recesses 11c and have semicircular-shaped ends. According to a second embodiment of the braking device 10, the last stator disc 11.5 is replaced by a last stator disc 11.5' illustrated in Figure 4A. The last stator disc 11.5' differs from the last stator disc 11.5 in that it comprises a rear face 11b' without a boss. The rear face 11b'and the front face 11a define a thickness e' of the last stator disc 11.5' which is greater than the thickness e of the last stator disc 11.5, the rear face 11b' being arranged to define with the torque tube 13 the minimum clearance J. Figures 4B and 4C illustrate last stator discs 11.5'', 11.5''' corresponding to variants of the last stator disc 11.5' illustrated in Figure 4A. The last stator discs 11.5'', 11.5''' differ from the last stator disc 11.5' in that they comprise a rear face 11b'', 11b''' defining with the front face 11a a thickness e'', e''' of said last stator discs 11.5'', 11.5''' which is different from the thickness e' of the last stator disc 11.5'. The thickness e'', e''' of the last stator discs 11.5'', 11.5''' is greater than the thickness e of the last stator disc 11.5 and the rear faces 11b'', 11b''' are arranged to define with the torque tube 13 the minimum clearance J. According to a third embodiment of thebraking device 10, the last stator disc 11.5 is replaced by a last stator disc 11.5'''' shown in Figure 5, and the torque tube 13 is replaced by a torque tube 13'. The last stator disc 11.5'''' differs from the last stator disc 11.5 in that it includes a rear face 11b'''' devoid of boss. The rear face 11b'''' and the front face 11a define a thickness of the last stator disc 11.5'''' which is equal to the thickness e of the last stator disc 11.5. The torque tube 13' differs from the torque tube 13 in that its first end is provided with boss 13e' extending opposite the rear face 11b'''' of the last stator disc 11.5''''. Each of the bosses 13e' extends between two neighboring pads 14 and comprises a main surface 13f' which extends in a plane parallel to the rear face 11b'''' of the last stator disc 11.5'''' and which is arranged to come to bear against said rear face 11b'''' in the event of axial creep of thestuds 14. The bosses 13e' thus form pads making it possible to take up and transfer the press force to the torque tube 13' in the event of failure of the studs 14. The main surfaces 13f' of the bosses 13e' are arranged to define with the rear face 11b'''' of the last stator disc 11.5'''' the minimum clearance J. Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims. The rim may be in one or more pieces. The number of stator discs and the number of rotor discs may be different from those illustrated. The number, shape and location of the studs 14 may be different from those illustrated. The number of actuators 18 may be equal to the number of pads 14 or different from said number of pads 14. The number, shape and location of the bosses 11e may be different from those illustrated. Although the actuators here are hydraulic,They can also be electric. Although the bosses 11th, 13th' are here made of the same material as the last stator disc 11.5, 11.5'''' and the torque tube 13, 13', they can also be added. Although the brake discs are here made of carbon, the bosses 11th, 13th' can be made of other materials such as steel, titanium, nickel / chromium / iron alloys such as those of the Inconel brand, a polymer such as polyetheretherketone (PEEK), a ceramic...

Claims

CLAIMS 1. Braking device (10) for an aircraft wheel (1) comprising: − a torsion tube (13, 13') extending along a longitudinal axis; − a stack of brake discs (11) comprising stator discs (11.1, 11.2, 11.3, 11.4, 11.5, 11.5', 11.5'', 11.5''', 11.5'''') and rotor discs (12.1, 12.2, 12.3, 12.4) stacked alternately on the torque tube, the stator discs comprising a first stator disc (11.1) and a last stator disc (11.5, 11.5', 11.5'', 11.5''', 11.5'''') between which intermediate stator discs (11.2, 11.3, 11.4) alternating with the rotor discs; − at least one actuator (18) which is fixed to a first end of the torque tube and which comprises a piston mounted movable in translation along an axis parallel to the longitudinal axis, between a first extreme position in which the piston is distant from the stack of discs and a second extreme position, to exert a pressing force on the first stator disc; and − at least one stud (14) arranged between a second end of the torque tube and the last stator disc to take up and transfer the pressing force to the torque tube; characterized in that the last stator disc and the torque tube are shaped to define between them, along the longitudinal axis, a minimum clearance which, for a given maximum wear of the discs, is less than the distance separating the piston from its second extreme position when said piston exerts the pressing force. 2.Braking device (10) according to claim 1, wherein the last stator disc (11.5) comprises at least one boss (11e) extending projecting from a rear face (11b) of the last stator disc (11.5), the boss. defining, with the torque tube (13), the minimum clearance (J).

3. Braking device (10) according to claim 2, wherein the boss (11e) comprises a main face (11f) extending in a plane orthogonal to the longitudinal axis, the main face defining, with the torque tube (13), the minimum clearance (J).

4. Braking device (10) according to claim 2 or 3, comprising a plurality of studs (14) equally distributed around the longitudinal axis, the last stator disc (11.5) comprising a plurality of bosses (11e) each extending between two neighboring studs.

5. Braking device (10) according to claim 4, wherein the bosses (11e) are in the shape of an arc of a circle and are inscribed in a circle whose center belongs to the longitudinal axis.

6. Braking device (10) according to claim 1, wherein the last stator disc (11.5', 11.5'', 11.5''', 11.5'''') has a rear face (11b', 11b'', 11b''', 11b'''') defining with the torque tube (13, 13'), the minimum clearance (J).

7. Braking device (10) according to claim 1, wherein the second end of the torque tube (13') has at least one boss (13e') defining, with the last stator disc (11.5''''), the minimum clearance (J).

8. Aircraft wheel (1) equipped with a braking device (1) according to any one of the preceding claims.

9. Aircraft landing gear (P) comprising at least one wheel (1) according to claim 8.

10. Aircraft (A) comprising at least one landing gear (P) according to claim 9.

Images