Wedge of a braked wheel of an aircraft

Description

BACKGROUND OF THE INVENTION

[0001] Aircraft wheels are known which are mounted on aircraft landing gears and are intended to cooperate with a brake. In general, the brake comprises discs which extend inside the wheel rim, including stator discs which are stopped from rotating and arranged alternately with stator discs which are driven in rotation by the wheel rim by bars secured to the rim and which extend into peripheral notches of rotor discs. Pressure applied to all the discs generates friction between the facing discs and therefore a braking torque which slows the rotation of the wheel.

[0002] The bars extend inside the wheel rim in a direction substantially parallel to an axis of rotation of the wheel. They may be integral with the wheel rim or attached to the latter, in various ways. Some known bars have at one end a cylindrical tail which is inserted into holes made in the rim web along an axis parallel to the axis of rotation of the wheel, while the other end has an orifice adapted to receive a screw extending in service along a radial axis and screwing into a threaded hole in the rim. The bar is then associated with a shim which is interposed between the bar and the rim to, on the one hand, position the bar in a direction parallel to the axis of rotation of the wheel and, on the other hand, contribute to limiting the heat flows between the stack of discs and the wheel rim.

[0003] Indeed, it is important to ensure that the temperature of the rim does not exceed temperatures that could be detrimental to the tire carried by the rim since the lugs are in contact with the rotor discs which can be brought to very high temperatures during certain braking. The rim, which is most often made of aluminum alloy, is conventionally protected by thermal shields which limit its heating by radiation. But the shim, which is in direct contact with the rim, constitutes a conduction path likely to cause local heating of the rim, all the more delicate as it occurs near the bead of the rim on which the tire rests.

[0004] Document US 2007 / 246995 discloses shims comprising two support blocks separated by a central core pierced to allow the screw for fixing the bar to the rim to pass through. Such a geometry optimizes the transfer of braking torque, by distributing the support pressure of the shim on the rim. However, it can give rise, at the level of the contacts of the support blocks on the rim, to occasional heating which should be limited. SUBJECT OF THE INVENTION

[0005] The invention aims to propose a wheel bar shim reducing the transfer of heat by the bar from the discs to the rim. PRESENTATION OF THE INVENTION

[0006] In order to achieve this aim, a wedge according to claim 1 is provided.

[0007] The recesses significantly reduce the ability of the blocks to conduct heat from the lug to the rim, without altering the transfer of torque to the rim. These recesses are easily produced using additive manufacturing techniques, in various geometries. DESCRIPTION OF FIGURES

[0008] The invention will be better understood in light of the following description of a particular embodiment of the invention, with reference to the figures of the appended drawings, among which: There Figure 1A is a longitudinal sectional view of a braked wheel mounted on an aircraft landing gear axle, the rim of which is equipped with bars with the interposition of a shim according to the invention. Figure 1B is a perspective view of one of the bars and its shim, showing its arrangement on the wheel rim; Figures 2A and 2B are perspective views of the wedge and the bar of the Figures 1A And 1B, as assembled in service; The Figures 3A to 3C are perspective, front and rear views which illustrate a wedge with hollow blocks according to a first particular embodiment of the invention; The Figures 4A to 4C are perspective views, from the front and from behind, which illustrate a wedge with hollow blocks according to a second particular embodiment of the invention; The Figures 5A to 5F are perspective views, from the front, from behind, then in section, which illustrate a wedge with hollow blocks according to a third particular embodiment of the invention; the Figure 5G is an enlargement of one of the internal motifs of the wedge; The Figures 6A to 6F are perspective views, from the front, from behind, then in section, which illustrate a wedge with hollow blocks according to a fourth particular embodiment of the invention; the Figure 6G is an enlargement of one of the internal motifs of the wedge; The Figures 7A to 7Fare perspective views, from the front, from behind, then in section, which illustrate a wedge with hollow blocks according to a fifth particular embodiment of the invention; Figure 7G is an enlargement of one of the internal motifs of the wedge; The Figures 8A to 8F are perspective views, from the front, from behind, then in section, which illustrate a wedge with hollow blocks according to a sixth particular embodiment of the invention; The Figures 9A to 9F are perspective views, from the front, from behind, then in section, which illustrate a wedge with hollow blocks according to a seventh particular embodiment of the invention; Figure 9G is an enlargement of one of the internal motifs of the wedge; The Figures 10A to 10F are perspective views, from the front, from behind, then in section, which illustrate a wedge with hollow blocks according to an eighth particular embodiment of the invention; Figure 10G is an enlargement of one of the internal motifs of the wedge; The Figures 11A to 11F are perspective views, from the front, from behind, then in section, which illustrate a wedge with hollow blocks according to a ninth particular embodiment of the invention.

[0009] In the figures, the X,Y,Z axes are relative to the shim and when the shim is in position on the rim, the X axis is parallel to the rotation axis Δ of the wheel, the Y axis is parallel to an orthoradial direction, and the Z axis is parallel to a radial direction. The directions mentioned below are given by the coordinates (a,b,c) of a direction vector in the (X,Y,Z) frame. DETAILED DESCRIPTION OF THE INVENTION

[0010] In reference to the Figures 1A to 2B, a braked aircraft wheel comprises a rim 1 mounted to rotate about an axis of rotation Δ on a landing gear axle 6 by means of bearings 7. The rim 1 receives a tire (not shown here) and defines a cavity in which a stack of brake discs 2 extends. The stack 2 comprises stator discs 2A stopped in rotation alternately with rotor discs 2B which are driven in rotation by the wheel by means of bars 3 which are fixed to the rim 1 and which cooperate with riders 4 of the rotor discs 2B protecting the notch flanks of the rotor discs 2B in which the bars 3 extend.Here, the bars 3 comprise an elongated body 3A which extends substantially in a direction parallel to the axis Δ and which comprises an end in the form of a cylindrical tail 3B which is received in an orifice 8 of the rim extending parallel to the axis X, and another end 3C which comprises a drilling 3D in a radial direction intended to receive a screw 9 for fixing the bar 3 to the rim 1.

[0011] A shim 10 is interposed between the bar 3 and the rim 1 to both maintain the bar in a position substantially parallel to the axis of rotation Δ, form a mechanical interface between the bar 3 and the rim 1, and form a thermal barrier to the conduction of heat from the bar 3 to the rim 1. All this is well known and is only recalled for the purpose of illustration.

[0012] Here, the shim 10 comprises two support blocks 11 defining two opposite support faces, namely a support face 12 against the rim 1 and a support face 13 against the bar 3. From the support face 13 against the bar 3 and at the rear face of the shim 10 project two studs 14 which have the function of centering the shim 10 on the bar 3. The support blocks 11 are here connected to each other by a core 15 which comprises a bore 16 to allow the passage of the fixing screw 9 of the bar 3 to the rim 1. In all the embodiments illustrated here, the support blocks 11 have oblique sides 19 so that the front face 17 of the shim 10 is smaller than its rear face 18.

[0013] According to the invention, the support blocks 11 are hollowed out according to a hollowing rate at least equal to 30% of their overall volume. Here, the term "overall volume" means the volume defined by the external dimensions of the support blocks 11, which is identical before and after hollowing. The hollows thus made considerably reduce the thermal conduction rate of the shim 10 and thus contribute to significantly limiting the heating of the rim 1 at the level of the support of the shim 10 on the rim 1. In all the embodiments detailed below, the hollows open at least onto the front face 17 and the rear face 18 of the shim 10, so as to create in the shims an air passage from one face to the other in the direction (1,0,0).

[0014] According to a first particular embodiment illustrated in Figures 3A to 3C, the support blocks 11 of the wedge 10 have been hollowed out by producing tubular channels 20 which extend in the direction (1,0,0) from the front face to the rear face. Here, eleven channels 20 have been provided in each of the support blocks 11, to obtain a hollowing rate of 33%. Compared to a solid wedge, the reduction in the heat flux transmitted by conduction by the wedge is estimated at 33%.

[0015] According to a second particular embodiment illustrated in Figures 4A to 4C , the support blocks 11 have been hollowed out by producing channels 21 which extend in the direction (1,0,0). Here, three channels with a diameter greater than that of the pipes 20 of the previous embodiment have been provided in each of the support blocks 11 to obtain a hollowing rate of 35%. Compared to a full wedge, the reduction in the heat flux transmitted by conduction by the wedge is estimated at 35%.

[0016] The channels 20, 21 can be obtained by drilling the support blocks 11 after manufacturing the shim 10. Alternatively, they can be obtained at the same time as the rest of the shim 10 by any additive manufacturing process.

[0017] According to a third particular embodiment illustrated in Figures 5A to 5G , the wedge 10 is obtained by additive manufacturing so as to provide inside the support blocks 11 a hollow lattice structure 22 whose elementary star pattern 23 is visible at the Figure 5G . Pattern 23 is here inscribed in a cube and has branches of constant section which radiate from the center of the cube towards the eight corners of the cube, therefore in the directions (1,1,1), (1,-1,-1), (-1,-1,1) and (-1,1,-1). Here, the elementary pattern 23 is duplicated 9 times in the direction (1,0,0). The patterns thus duplicated are juxtaposed with each other in two layers parallel to the XY plane. One of the layers is visible on the Figures 5D and 5Fwhere the wedge was cut along a median plane parallel to the XY plane. Here, the hollowed-out structure leads to a hollowing rate of the support blocks 11 of 47%. Compared to a solid wedge, the reduction in heat flow transmitted by conduction through the wedge is estimated at 60%.

[0018] According to a fourth particular embodiment illustrated in Figures 6A to 6G , the wedge 10 is obtained by additive manufacturing so as to provide inside the blocks 11 a hollow lattice structure 24 whose elementary star pattern 25 is visible at the Figure 6G. The pattern 25 is similar to that of the previous embodiment. However, the cube in which the pattern 25 is inscribed here has a side twice that of the previous embodiment, so that the patterns 25 are juxtaposed in a single layer parallel to the XY plane. The hollowed-out structure leads to a hollowing rate of the support blocks 11 of 51%. Compared to a solid shim, the reduction in the heat flux transmitted by conduction by the shim is estimated at 63%.

[0019] According to a fifth particular embodiment illustrated in Figures 7A to 7G , the wedge 10 is obtained by additive manufacturing so as to provide inside the blocks 11 a hollow lattice structure 26 whose elementary tetrahedron pattern 27 is visible at the Figure 7G and comprises branches with constant section, one branch of which extends in the direction (0,0,1) and an opposite branch of which extends in the direction (1,0,0). This pattern is duplicated in the directions (1,0,0), 1 2 1 , 1 , 2 , − 1 This hollowed-out structure results in a hollowing rate of the support blocks 11 of 53%. Compared to a solid wedge, the reduction in heat flow transmitted by conduction through the wedge is estimated at 67%.

[0020] According to a sixth particular embodiment illustrated in Figures 8A to 8F , the wedge 10 is obtained by additive manufacturing so as to provide inside the blocks 11 a tetrahedron structure 28 whose elementary pattern comprises branches with constant section, one branch of which extends in the direction (0,1,0) and an opposite branch in the direction (1,0,0). This pattern is duplicated in the directions (1,0,0), 1 1 2 , 1 , − 1 , 2 . In this embodiment, the recesses thus made also open onto the sides 29 of the blocks 11. This hollowed-out structure gives rise to a hollowing rate of the support blocks 11 of 37%. Compared to a solid shim, the reduction in the heat flow transmitted by conduction by the shim is estimated at 44%.

[0021] According to a seventh particular embodiment illustrated in Figures 9A to 9G , the wedge 10 is obtained by additive manufacturing so as to provide inside the blocks 11 a hollow lattice structure 30 whose elementary tetrahedron pattern 31 is visible at the Figure 9G and comprises branches with a constant section, one branch of which extends in the direction (0,1,0) and an opposite branch in the direction (1,0,0). This pattern is duplicated in the directions (1,0,0), 1 1 2 , 1 , − 1 , 2 This hollowed-out structure results in a hollowing rate of the support blocks of 37%. Compared to a solid wedge, the reduction in heat flow transmitted by conduction through the wedge is estimated at 46%.

[0022] According to an eighth particular embodiment illustrated in Figures 10A to 10G, the wedge 10 is obtained by additive manufacturing so as to provide inside the blocks 11 a hollow lattice structure 32 whose elementary tetrahedron pattern 33 is visible at the Figure 10G and includes branches with constant section, one branch of which extends along the direction (0,0,1) and one face extends parallel to the plane (Y,Z). This pattern is duplicated along the directions (0,0,1), 1 2 1 , − 2 2 , 1 , 3 . This hollowed-out structure gives rise to a hollowing rate of the support blocks of 44%. The reduction in the heat flow transmitted by conduction by the wedge is estimated at 57%. According to a ninth particular embodiment illustrated in Figures 11A to 11F, the shim 10 is obtained by additive manufacturing so as to provide inside the support blocks 11 a hollow lattice structure 34 whose elementary tetrahedron pattern is similar to that of the previous embodiment. In this embodiment, the recesses also open onto the sides 19 of the blocks 11. This hollow structure leads to a hollowing rate of the support blocks 11 of 46%. Compared to a solid shim, the reduction in the heat flux transmitted by conduction by the shim is estimated at 62%.

[0023] Removing the support blocks by at least 30% allows for a dramatic reduction in the heat flow transmitted by conduction through the shim from the bar to the rim, while preserving the shim's ability to transmit braking torque. Distributed recessed structures defining recesses that open onto the front and rear faces of the shim and that provide a path between the two faces will be preferred, allowing air to circulate inside the shim, particularly under the effect of forced air circulation imposed by a brake cooling fan. The recesses can also open onto the sides of the shim as well as onto the Figures 8A Or 11A .

[0024] The invention is not limited to what has just been described, but on the contrary encompasses any variant falling within the scope defined by the claims. In particular, although the recesses are here obtained by tubular channels or by repetition of hollowed-out branch patterns, any other geometry may be envisaged as long as it gives rise to a hollowing rate of the support blocks at least equal to 30%.

Claims

1. A bar spacer (10) for a braked aircraft wheel intended to be interposed between a rim(1) and a bar (3) fitted to the rim in order to drive the rotor disks of the brake in rotation, the spacer comprising two bearing blocks (11) connected together by a core (15) that is pierced to pass a screw for fastening the bar to the rim, the spacer comprising a front face (17) and a rear face (18) with reference to a longitudinal direction of the bar bearing against the bar spacer, characterized in that the bearing blocks (11) of the spacer include voids defining a void fraction of at least 30% of an overall volume of the bearing blocks, the overall volume of the bearing blocks being identical with and without the voids, and the voids opening out in the front face and the rear face of the spacer in order to provide an air passage in the spacer between said front face and said rear face.

2. A bar spacer according to claim 1, wherein the voids open out in flanks (19) of the spacer.

3. A bar spacer according to claim 1, wherein the voids are obtained by making tubular channels (20; 21) in the blocks, the channels extending from the front face (17) to the rear face (18) of the spacer.

4. A bar spacer according to claim 1, wherein the voids are obtained by means of a hollowed-out structure defined by repeating a branching pattern (23; 25; 27; 30; 31; 33) and that extends from the front face (17) to the rear face (18) of the spacer.

5. A bar spacer according to claim 4, wherein the pattern is a star pattern (23; 25) inscribed in a cube having branches radiating from the center of the cube towards the eight corners of the cube.

6. A bar spacer according to claim 4, wherein the elementary pattern is a tetrahedral pattern (27; 30; 31; 33).

7. An aircraft wheel rim, the rim being fitted with bars (3) fastened to the rim with interposed bar spacers according to any preceding claim, each bar being held in abutment against one of the spacers by the screw fixing the bar to the rim.