BAR FOR A BRAKED AIRCRAFT WHEEL

The invention relates to a bar (10) for a braked aircraft wheel (103), the bar being for fitting to a rim (104) of the wheel in order to drive rotor brake disks (106b) in rotation. The bar comprises a substantially rectilinear body (11) having at least one segment (14) including two wings (15) connected together by a core (16) and intended to co-operate with the rotor disks. At least one brace element (17) connects a free edge of each of the wings to a central portion of the core.

The present invention relates to the field of aviation and, more particularly, to braking aircraft wheels.

BACKGROUND OF THE INVENTION

Aircraft wheels are known that are mounted on undercarriages and that are provided with respective brakes. Such a brake generally comprises stator disks arranged in alternation with rotor disks that are driven in rotation by Inconel® alloy bars secured to the inner periphery of a rim of the wheel. The bars are received in peripheral notches in the rotor disks, and they extend in a direction that is substantially parallel to the axis of rotation of said wheel. Controlled pressure applied to the stack of disks gives rise to friction between the facing disks, and thus to a braking torque that slows down the rotation of the wheel.

The bars may be made integrally with the rim of the wheel, or they may be fitted thereto. With reference toFIG. 1A, certain prior art bars1have a cylindrical tail at one end1afor engaging in orifices made in a disk or “web” of the rim, and at an opposite end1bthey have an orifice arranged to receive a screw that is screwed into a tapped orifice in the rim. Titanium wedges2are interposed between the bars1and the rim, firstly in order to position the bars1in a direction parallel to the axis of rotation of the wheel, and secondly in order to contribute to limiting the transfer of heat between the brake disks and the rim, which could be harmful for a tire mounted on said rim.

As shown inFIG. 1B, the bars1sometimes present an H-shaped cross-section that is broadly constant. Such a cross-section serves to withstand the stresses induced by braking and in particular the shear and bending stresses generated by slowing down the rotor disks.

By way of example, such bars are known from Document FR-A-2 937 949.

A braked aircraft wheel may have seven to eleven bars1, depending on the size of the wheel. For an aircraft having two to six wheels per undercarriage and for a bar1weighing 500 grams (g) to 800 g, it can be seen that the bars contribute significantly to the overall weight of the wheel-and-brake assembly.

However, lightening aircraft has become an imperative for all aircraft manufacturers, particularly since regulations have been encouraging them to do so. Specifically, environmental standards require reduction in emissions of pollutants, and in particular of carbon dioxide (CO2).

OBJECT OF THE INVENTION

An object of the invention is thus to propose a bar for a braked aircraft wheel that makes it possible in particular to reduce the weight of the wheel-and-brake assembly of an aircraft without degrading the mechanical strength of said bar.

SUMMARY OF THE INVENTION

For this purpose, the invention provides a bar for a braked aircraft wheel, the bar being for fitting to a rim of the wheel in order to drive rotor brake disks in rotation. The bar comprises a substantially rectilinear body having at least one segment including two wings connected together by a core and intended to co-operate with the rotor disks.

According to the invention, the bar includes at least one brace element connecting a free edge of each of the wings to a central portion of the core.

Such brace elements enable the thicknesses of the wings and of the core to be optimally determined, thereby enabling the overall weight of the bar to the reduced without degrading its mechanical strength.

In a particular embodiment, the brace element is a wall extending in a longitudinal direction of the bar between said free edge and the central portion of the core.

According to a particular characteristic, a portion of the body forms a fastener wedge for fastening the bar to the rim.

There is thus no longer any need to provide an operation of adding a wedge while putting the bar into place, thereby limiting the number of operations needed for putting the bar into place on the rim of the wheel.

Advantageously, the wedge includes recesses, thereby enabling the overall weight of the bar to be limited and also limiting the transfer of heat to the rim.

According to another particular characteristic, a portion of the body includes a trellis structure.

The invention also provides a braked aircraft wheel comprising a rim having an inner periphery defining a space for receiving both rotor brake disks and also such bars fastened to the rim in order to constrain the rotor brake disks to rotate with the rim.

The invention also provides landing gear including at least one such wheel and an aircraft including such landing gear.

The invention also provides a method of fabricating such a bar, the method comprising at least one operation of fabricating the body of the bar by additive fabrication.

In a particular implementation, the additive fabrication operation is performed in such a manner as to obtain the bar in a vertical position.

Alternatively, the additive fabrication operation is performed in such a manner as to obtain the bar in a horizontal position and it includes a step of making a trellis supporting a wall of the body of the bar.

Preferably, the additive fabrication operation makes use of laser beam melting on a bed of powder.

In particular manner, the powder is an Inconel® alloy powder.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIGS. 2 and 3, an aircraft100of the invention comprises a structure provided with undercarriages101. Each undercarriage101comprises a leg having one end hinged to the structure of the aircraft100and an opposite end carrying an axle102on which a wheel103is rotatably mounted.

The wheel103comprises a rim104and a web105connecting the rim104to a hub that is rotatably received on the axle102so that an inside surface of the rim104extends facing an outside surface of the hub and co-operates with the hub to define a space for receiving a stack of brake disks. The stack comprises stator disks106aprevented from rotating relative to the leg of the undercarriage and rotor disks106bincluding peripheral notches that receive bars, given overall reference10, which bars are fastened to the inside surface of the rim104.

With reference toFIG. 4A, each bar10comprises a body11extending along a longitudinal axis X. The body11has a first end11ain the form of a cylindrical tail that is to be received in an orifice of the rim104extending parallel to the axis of rotation of the wheel103, and a second end11bincluding a hole12in a radial direction for receiving a fastener screw for fastening the bar10to the rim104.

The body11also has two lateral bearing faces13extending parallel to the axis X for the purpose of cooperating with clips arranged in the peripheral notches of the rotor brake disks106b.The two bearing faces13form a nonzero angle a so that in service they extend radially relative to the rim104. High velocity oxy fuel (HVOF) surface treatment is applied to the bearing faces13in order to obtain appropriate tribological behavior between the bar10and the clips. All this is well-known and it is recalled merely for information purposes. Between the first end and the second end, and as shown inFIG. 4B, the body11includes a segment14that presents a cross-section that is broadly constant and symmetrical about a midplane of the body11. The cross-section is substantially H-shaped and the segment14thus comprises two wings15having inside faces that are connected together by a core16and outside faces that form the bearing faces13. Each wing15has a bottom portion15aand a top portion15b,which portions extend on opposite sides of the core16. In this example, the top portions15bof the wings15present a height that is greater than the height of the bottom portions15a.In this example, the height of the top portions15bof the wings15is substantially equal to four times the height of the bottom portions15aof the wings15. The distance between the free edges of the top portions15bof the wings15is slightly greater than the distance between the free edges of the bottom portions15aof the wings15.

Furthermore, brace elements17connect the free edges of the top portions15bof the wings15to a central portion of the core16. Each brace element17has a wall with a plane zone17aextending between the central portion of the core16and a rounded zone17bthat connects the plane zone17ato the free edge of the top portion15bof one of the wings15. Relative to the core16, the plane zone17aof each brace element17forms an angle β that is substantially equal to 45° in this example. The brace elements17serve to oppose any tendency of the wings15to be deformed or overturned while the bar10is in service, thereby enabling the thickness of the wings15and of the core16to be optimized.

A portion of the end11bof the body11is shaped to constitute a fastener wedge18for fastening the bar10to the rim104. The wedge18is thus made integrally with the bar10and the hole12passes through its center in order to be able to pass the fastener screw for fastening the bar10to the rim104. At its top portion, the wedge18has two plane bearing faces18aextending in the same plane for the purpose of cooperating with a plane surface of the rim104. The two bearing faces18aare arranged symmetrically on either side of the hole12.

With reference toFIGS. 4C and 4D, the wedge18is hollowed out by making two channels18bthat extend on either side of the hole12substantially in a longitudinal direction relative to the bar. The channels18bhave several functions: they enable air to flow inside the wedge18, in particular under the effect of a forced flow of air imparted by a brake cooling fan, and their presence limits the quantity of material of the wedge18that enables heat to be transferred by conduction from the rotor brake disks106bto the rim104.

The channels18bthus reduce considerably the rate of heat conduction by the wedge18, thereby contributing to significantly limiting the temperature rise of the rim104, in particular where the bearing faces18aof the wedge18bear against the rim104, while preserving the ability of the wedge18to transmit braking torque to the rim104.

The bar10is made by additive fabrication vertically along its axis X, and more particularly fabrication by laser beam melting (LBM) on a bed of metal powder. The bar10is then obtained in the vertical position. This method enables the bar10to be fabricated in a single operation on the basis of a three-dimensional (3D) digital file for said bar10. The bar10is constructed by using selective melting of a powder of Inconel® alloy under a controlled atmosphere. The Inconel® alloy powder is spread by a scraper to form a bed of varying thickness in the range 30 micrometers (μm) to 90 μm. An optical fiber laser beam is steered by mirrors to scan the bed so as to melt the powder selectively in zones that are defined upstream by the 3D digital file. By way of example, the laser beam may be an yttrium aluminum garnet (YAG) laser beam.

In comparison with the bar1and for an identical fastener interface, the bar10makes it possible to achieve a weight saving for the bar-and-wedge assembly that lies in the range 15% to 20%. Furthermore, the mechanical strength and in particular the bending strength of the bar is improved.

Naturally, the invention is not limited to the implementations described, but covers any variant coming within the ambit of the invention as defined by the claims.

The body11of the bar10need not be integral with the wedge, but could have a bearing face arranged to receive a wedge that is fitted on the bar.

In order to increase the stiffness of the bar10, and also in order to enable the bar10to be additively fabricated from a powder in such a manner as to obtain the bar horizontally, a portion of the body11of said bar10may include a lattice structure19, as shown inFIG. 5, in other words a hollowed-out trellis structure with a unit pattern that may for example be a tetrahedron, and that serves to support a wall of the bar.

The brace elements17may be of a shape other than those shown inFIG. 4B.

Although in this example the bar10is made by additive fabrication, it could also be made by other methods, e.g. by lost wax casting.

Powders other than Inconel® alloy powder could be used for fabricating the bar10, in particular depending on the operating requirements for said bar (e.g. steel powder . . . ).