Heat shield for aircraft wheel brakes

Abstract

The invention relates to a braking device (1) for an aircraft wheel, comprising a ring (15) having a plurality of cavities (17) in which actuators (18) are mounted to apply a braking force to a stack of discs (11) extending opposite the ring. The ring is provided with a heat shield (25) extending opposite the face of the ring directed towards the stack of discs to protect the ring from the heat radiation generated by the stack of discs. According to the disclosure, the heat shield is provided with a hole (26) through which the actuator extends and has a cross-sectional profile formed to reflect the heat radiation away from the device.

Description

Technical Field

[0001] The present invention relates to the field of aircraft wheel braking and, more particularly, to the control of heat transfer during braking. Background Art

[0002] An aircraft wheel comprises a rim surrounded by a tyre and connected by a web to a central hub intended to be rotatably mounted on an axle or spindle carried by the lower end of an aircraft landing gear strut. The wheel is provided with brakes. Such a wheel is known, for example, from document FR-A-2990188.

[0003] A brake for braking an aircraft wheel generally comprises an aluminum hydraulic ring having a cavity in which a brake actuator is mounted. Each actuator comprises a piston mounted in a sliding and sealing manner about a sliding axis, and the ring comprises a channel for distributing a pressurized hydraulic fluid to each actuator to push the piston, thereby exerting a braking force on a friction element extending relative to the ring. The friction element comprises a stator disc and a rotor disc alternately stacked on a torsion tube coaxial with the hub of the wheel. The ring is integral with the torsion tube by a thread, the stator disc is rotatably fixed to the torsion tube, and the rotor disc is rotatably integral with the rim of the wheel.

[0004] The heat release after friction of the discs can be significant, especially when the energy dissipated during braking is high (due to the mass and high speed of the vehicle when landing) and leads to overheating of the brake and its environment. If the materials constituting the rings and actuators are well resistant to this significant heat release, this is in contrast to the hydraulic fluid circulating in the rings, for which overheating would not only reduce its efficiency but also its service life. These effects affect the periodicity of the hydraulic fluid changes, which would increase the time the vehicle is stationary on the ground.

[0005] It is known to arrange a metal thrust plate between the piston and the disc stack to limit the heat exchange between the torsion tube and the ring. However, such a plate has proven to be not very effective and results in a significant increase in mass.

[0006] It has also been considered to insert a phenolic resin sheet between the torsion tube and the ring, in order to jointly limit the heat exchange by conduction. If such a sheet proves to be light and effective, it is not possible to ensure the correct tightening of the torsion tube on the ring.

[0007] A heat shield is also arranged between the ring and the wheel disc stack, which extends from the torsion tube to the actuator. However, this heat shield only partially covers the surface of the ring facing the wheel disc, so that its effectiveness in protecting the ring from heat radiation after the wheel disc friction is limited. Summary of the invention

[0008] The object of the present invention is to provide a heat shield capable of at least partially overcoming the above-mentioned problems.

[0009] To achieve this object, the invention proposes a braking device for an aircraft wheel, comprising a ring having a plurality of cavities into which actuators are fitted in order to exert a braking force on a stack of wheel discs extending opposite the ring.

[0010] According to the invention, the ring is provided with a heat shield extending opposite the face of the ring directed towards the stack of disks to protect the ring from the heat radiation generated by the stack of disks. The heat shield is provided with a hole through which the actuator extends and has a cross-sectional profile formed to reflect the heat radiation outside the device.

[0011] Such a heat shield makes it possible to limit the temperature increase of the ring due to the heat release generated by the friction of the discs when the brakes are applied. Thus, when the ring is arranged to distribute pressurized hydraulic fluid to each actuator, the temperature increase of the hydraulic fluid is also found to be limited, which makes it possible to maximize its efficiency and its service life.

[0012] According to particular characteristics, the heat shield comprises at least one surface portion inclined relative to the central axis of the ring.

[0013] Specifically, the inclined surface portion is curved.

[0014] Specifically, the inclined surface portion is flat.

[0015] According to another particular feature, the heat shield is a single piece and is held on the ring by being clamped between the ring and the torsion tube on which the stack of discs is stacked.

[0016] According to another particular feature, the heat shield comprises a reinforcement arranged between each hole.

[0017] In particular, the reinforcement is a stamped ridge.

[0018] According to another particular feature, the heat shield is made of a heat-insulating material.

[0019] Specifically, the face of the heat shield directed toward the ring is coated with a low-emissivity material.

[0020] According to another particular feature, the heat shield comprises, at the periphery, an outwardly turned edge extending towards the ring.

[0021] According to another specific feature, each hole comprises, at the periphery, an outer flange extending towards the stack of wheel discs.

[0022] According to another particular feature, the heat shield comprises a tubular portion extending from the edge of the hole towards the disc stack so as to partially surround the actuator and protect it from the thermal radiation generated by said disc stack.

[0023] The invention also relates to an aircraft wheel provided with such a braking device.

[0024] The invention also relates to an aircraft landing gear comprising at least one such wheel.

[0025] The invention also relates to a heat shield for a braking device for an aircraft wheel, the heat shield being intended to extend between a ring and a stack of disks of the device. The heat shield comprises holes through which an actuator mounted in a cavity of the ring extends in use, and has a cross-sectional profile formed so as to reflect, in use, heat radiation generated by the stack of disks away from the braking device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention will be better understood from the following description, which is purely illustrative and not restrictive and should be read with reference to the accompanying drawings, in which:

[0027] Figure 1 is an axial cross-sectional view of an aircraft wheel provided with a braking device according to a specific embodiment of the present invention;

[0028] Figure 2 yes Figure 1 a perspective view of the wheel, showing the distribution of the actuators of the braking device about the axis of rotation of the wheel;

[0029] Figure 3 Yes Figure 1 a perspective view of the brake device of the wheel shown without the actuating disc stack;

[0030] Figure 4 Yes Figure 1 A perspective view of a heat shield of a brake device for a wheel is shown;

[0031] Figure 5 Shows Figure 4 A first variation of the heat shield shown in , wherein the outer turn-over edge at the outer periphery of the heat shield has been extended;

[0032] Figure 6 Shows Figure 4 A second variation of the heat shield shown in , wherein the outer turned edge of the heat shield where the hole is provided has been extended; DETAILED DESCRIPTION

[0033] refer to Figure 1 and Figure 2 The present invention relates to a braking device (generally indicated by 1) for equipping an aircraft wheel 2.

[0034] The wheel 2 comprises two half-wheels 2a, 2b, each of which comprises an annular rim 3a, 3b connected by webs 4a, 4b to half-hubs 5a, 5b pivotally received on an axle or spindle 6 by means of bearings 7, 8. The half-wheel 2a comprises a groove formed in the edge of the rim 3a and has a sealing gasket 9 arranged therein so that the sealing gasket 4 is elastically compressed between the two half-wheels 2a, 2b once the two half-wheels 2a and 2b are assembled together.

[0035] The half-wheels 2a and 20b move towards each other in a direction parallel to the axis of rotation X of the wheel 2 and they comprise centering surfaces to ensure that the two half-wheels 2a and 2b are correctly positioned relative to each other. The half-wheels 2a, 2b are held in place by assembly bolts 10 arranged in facing holes formed in the webs 4a, 4b.

[0036] The bolts 10 are tightened in a known manner to assemble the wheel halves 2a, 2b together after mounting the tire (not shown) on the rims 3a, 3b. In this position, the sealing gasket 9 is elastically compressed between the wheel halves 2a, 2b, thus preventing the gas contained in the volume delimited by the tire 10 and the wheel halves 2a, 2b from escaping outside the wheel 2.

[0037] The brake device 1 comprises a brake disc 11, whose stator discs 11a and rotor discs 11b are stacked alternately against each other on a torsion tube 12, which is fixed to the housing 13 of the axle. The torsion tube 12 and the disc stack 11 extend inside the half wheel 2a in an annular space defined by the inner surface of the rim 3a, the web 4a and the outer surface of the half hub 5a.

[0038] The stator disk 11a is rotationally fixed relative to the axle 6, and the rotor disk 11b comprises axial peripheral recesses, each of which accommodates a section of a rod 14 fixed to the inner surface of the rim 3a. The rod 14 extends along an axis parallel to the axis of rotation X of the wheel 2 and ensures the rotational coupling of the rotor disk 11b with the rim 3a about said axis X.

[0039] The braking device 1 also comprises a hydraulic ring 15, which is fixed to the end of the torsion tube 12 by means of screws 16. The ring 15 comprises a plurality of cavities 17, which are symmetrically distributed around the axis of rotation X of the wheel 2 and are connected together by channels 15a. Each cavity 17 receives an actuator 18 which selectively applies a braking force to the stack of wheel discs 11 via a pressurized hydraulic fluid that circulates inside the ring 15 through the channels 15a.

[0040] The actuator 18 comprises a substantially cylindrical sleeve 19 which is sealingly housed in the cavity 17 of the ring 15. To this end, a sealing gasket 20 engages with the external face of the sleeve 19 to contain the hydraulic fluid in the cavity 17.

[0041] The piston 21 is mounted to slide in the sleeve 19 about a sliding axis parallel to the axis of rotation X of the wheel 2. To this end, the proximal end of the piston 21 comprises a projection formed as a bearing, which extends adjustably against the inner face of the sleeve 19 and accommodates a sealing gasket 22. The distal end of the sleeve 19 is formed as a bearing for guiding the piston 21 and is provided with a scraper 23. The end of the piston 21 accommodates a sliding shoe 24 to push against the first stator wheel disc 11a of the wheel disc stack 11. The annular distribution of the actuators 18 makes it possible to evenly distribute the braking force over the entire surface of the first stator wheel disc 11a.

[0042] The braking device 1 is provided with a heat shield 25 extending between the ring 15 and the stack of discs 11 in order to protect said ring 15 from heat radiation caused by the friction of the discs 11 during braking of the wheel 2 .

[0043] like Figure 3 As shown, the heat shield 25 is formed from a single piece of sheet material, in this case with a thickness of about 0.7 mm. The heat shield 25 is mainly annular in shape. A peripheral portion 25.1 of the heat shield 25 extends between the torsion tube 12 and the rim 3a and has a cross-sectional profile with a constant slope α relative to the central axis of the ring 15, which is coaxial with the axis X. The portion 25.1 includes holes 26, through each of which one of the actuators 18 extends.

[0044] As indicated by the arrows, the heat radiation generated by the friction of the wheel disc 11 is reflected on the opposite portion 25.1 of the heat shield 25 and acquires a radial component due to the slope α, which causes a portion of the radiation to return away from the rim 3a. In addition, the flared shape of the portion 25.1 causes the air contained between the wheel disc and the heat shield 25 to move naturally toward the outside, which is beneficial to the cooling of the wheel disc 11.

[0045] In order to improve the thermal insulation performance of the heat shield 25, the surface of the portion 25.1 directed toward the ring 15 may be coated with a low-emissivity material.

[0046] In order to limit deformations and vibrations of the heat shield 25, the portion 25.1 of the heat shield 25 comprises reinforcements 27 distributed symmetrically around the axis X between each hole 26. In this case, the reinforcements 27 are T-shaped stamped ridges.

[0047] Furthermore, portion 25.1 comprises at the periphery an outer lip 28 extending towards ring 15 and forming a slope β with respect to the central axis of ring 15. The outer lip 28 is oriented towards rim 3a and makes it possible to rigidify heat shield 25 and also limit the risk of cutting off the operator.

[0048] Furthermore, each hole 26 comprises, at the outer periphery, an outwardly turned rim 29 extending towards the wheel stack 11. The outwardly turned rim 29 makes it possible to improve the rigidity of the heat shield 25 in the vicinity of the hole 26.

[0049] according to Figure 5 and 6 , the outer rim 28 and / or the outer rim 29 can be extended to form a tubular portion 28', 29', respectively, making it possible to improve the thermal radiation protection of the ring 15 and to partially protect its jacket 19 and the piston 21 of the actuator 18. In order to facilitate the manufacture of such a heat shield 25, the tubular portions 28', 29' can be composed of a piece assembled on the portion 25.1. Thus, the heat shield 25 will no longer be made in one piece.

[0050] Furthermore, the heat shield 25 comprises an inner peripheral portion 25.2 clamped between the torsion tube 12 and the ring 15. The portion 25.2 extends in a plane substantially orthogonal to the axis X and comprises a hole 30 for the passage of the fixing screw 16. The portion 25.2 is connected to the portion 25.1 via a connection interface 25.3 which is mainly flared. The portion 25.2 makes it possible to fix the heat shield in place in the braking device 1 and to limit the heat exchange by conduction between the torsion tube 12 and the ring 15 (e.g. Figure 1 (indicated by the double arrows).

[0051] In order to limit these heat exchanges more effectively, it is possible to arrange a gasket made of insulating material between the portion 25 . 2 and the ring 15 , or to coat the portion 25 . 2 with a low-emissivity material.

[0052] Of course, 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.

[0053] The rim can be made up of one or more parts.

[0054] Although in this case the heat shield is made in a single piece, it may comprise multiple pieces, for example a series of petals extending around the central axis of the ring.

[0055] Although in this case the slopes α and β of the heat shield are constant, they may be variable, whereby the face of the ring directed towards the disc stack is of curved shape.

[0056] The heat shield can have a thickness varying from 0.7 mm, depending on the material it is made of.

[0057] Depending on the available space between the ring and the disc stack, the slope α can be made to vary.

[0058] The heat shield may be made of insulating material, for example of polyetheretherketone, cork, ceramic or of a composite material such as the composite material based on a glass-ceramic matrix, reinforced with silicon carbide and commercialized by the company Pyromeral Systems under the trademark PyroSic.

[0059] The number and size of the holes in the heat shield may vary from that shown.

[0060] The number, shape and placement of reinforcement members 27 may vary from that shown.

Claims

1. A braking device (1) for an aircraft wheel, comprising a ring (15) having a plurality of cavities (17) into which actuators (18) are fitted in order to apply a braking force to a stack of disks (11) extending opposite to the ring, the ring being provided with a heat shield (25) extending opposite to a face of the ring directed towards the stack of disks in order to protect the ring from heat radiation generated by the stack of disks, the heat shield being provided with holes (26) through which the actuators extend and having a cross-sectional profile formed to reflect the heat radiation away from the device, characterized in that The heat shield is held on the ring (15) by being clamped between the ring and a torsion tube (12) on which the stack of disks (11) is stacked.

2. The braking device (1) according to claim 1, characterized in that The heat shield (25) comprises at least one inclined surface portion (25.1) relative to the central axis of the ring.

3. The brake device (1) according to claim 2, characterized in that The inclined surface portion (25.1) is curved.

4. The braking device (1) according to claim 2, characterized in that The inclined surface portion (25.1) is flat.

5. The brake device (1) according to claim 1, characterized in that The heat shield (25) is made of a single piece.

6. The brake device (1) according to claim 1, characterized in that The heat shield (25) includes a reinforcement member (27) arranged between each of the holes (26).

7. The braking device (1) according to claim 6, characterized in that The reinforcement (27) is a stamped ridge.

8. The brake device (1) according to claim 1, characterized in that The heat insulation cover (25) is made of heat insulation material.

9. The brake device (1) according to claim 1, characterized in that The surface of the heat shield (25) directed toward the ring is coated with a low emissivity material.

10. The brake device (1) according to claim 1, characterized in that The heat shield (25) comprises an outer lip extending toward the ring (15) at the outer periphery.

11. The brake device (1) according to claim 1, characterized in that Each of the holes comprises at the periphery an outer lip (29) extending towards the wheel disc stack.

12. The brake device (1) according to claim 1, characterized in that The heat shield (25) comprises a tubular portion (29') extending from the edge of the hole towards the disc stack to partially surround the actuator and protect it from the heat radiation generated by the disc stack.

13. Aircraft wheel (2) provided with a braking device (1) according to any one of claims 1 to 12.

14. Aircraft landing gear comprising at least one aircraft wheel according to claim 13.

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