VARIABLE PITCH BLADE FOR AN AIRCRAFT TURBOMACHINE PROPELLER

Abstract

Variable-pitch blade (10) for an aircraft turbomachine propeller, comprising a blade (12) connected by a stilt (30) to a root (14) which is centered on a blade pitch axis (A), the blade (10) being made of composite material from at least one metal body (50) and a fiber preform (52) obtained by three-dimensional fiber weaving and embedded in a polymer matrix which ensures the attachment of the preform (52) to the metal body (50), the metal body (50) forming at least the root (14) and the stilt (30), and the fiber preform (52) forming at least the blade (12) which comprises a lower surface (12a) and an upper surface (12b) connected to each other by leading (12c) and trailing (12d) edges of the blade (12). Figure for abstract: Figure 4

Description

Title of the invention: VARIABLE PITCH BLADE FOR AN AIRCRAFT TURBOMACHINE PROPELLER Technical field of the invention

[0001] The present invention relates to the field of aircraft turbomachines and in particular to the propulsion propellers of these turbomachines which comprise variable-pitch blades. Technical background

[0002] The state of the art includes in particular documents FR-A1-3 017 163, FR-A1-3 080 322 and WO-A1-2023 / 031522.

[0003] The search for minimizing polluting emissions linked to air transport involves in particular the improvement of all the efficiencies of turbomachine propulsion systems, and more particularly the propulsive efficiency which characterizes the efficiency with which the energy which is communicated to the air which passes through the engine is converted into useful thrust force.

[0004] The elements influencing this propulsive efficiency in the first order are those linked to the low pressure parts of the propulsion system, which contribute immediately to the generation of thrust: low pressure turbine, low pressure transmission system, fan and secondary flow guiding the flow of the latter. The known guiding principle for improving the propulsive efficiency consists of reducing the compression ratio of the fan, thereby reducing the flow speed at the engine outlet and the kinetic energy losses linked to it.

[0005] One of the main consequences of this reduction in flow speed at the engine outlet is that it is necessary to process a higher mass flow of air in the low pressure part (secondary flow) in order to ensure a given thrust level, set by the characteristics of the aircraft: this therefore leads to an increase in the engine bypass ratio. The bypass ratio, or BPR (ByPass Ratio, in English) is defined as the ratio between the mass flow passing through the secondary flow (cold flow), and the mass flow passing through the primary flow (hot flow) and supplying in particular the combustion chamber.

[0006] This increase in secondary flow has the direct effect of requiring an increase in the diameter of the fan, and consequently the external dimensions of the retention casing surrounding it, as well as the nacelle constituting the aerodynamic envelope of the casing in question. To aim for high dilution rates, the casing becoming too large and too heavy (and generating significant capture drag), the latter is removed to move to configurations with unducted propellers. Several unducted turbomachine concepts would be possible, such as the Unducted Single Fan (USF) architecture: unducted turbomachine with (at least) one upstream variable-pitch propeller wheel (or "Open Fan") and a downstream rectifier wheel (stator) with fixed or variable pitch.

[0007] The technical field of the present invention lies within the framework of propeller or fan blades, rotating (rotor), shrouded or unshrouded and with variable pitch, with potential application in the aeronautical propulsion industry. Other examples of architectures particularly concerned: Contra-Rotating Open Rotor (CROR) and turboprop.

[0008] On unducted architectures (USF, CROR and turboprop), intense vibration excitation occurs at high rotation speeds due to the effects of engine installation on the aircraft and the direction of the upstream infinite flow. Indeed, an unducted engine is subject to the influence of the ground and the fuselage, which causes a distortion in the supply of the propeller, in flow speed, according to the engine azimuths. This results in a vibration response of the propeller blades on the first engine orders "IN", "2N" and "3N" (possibly more).

[0009] On the other hand, in the absence of an air inlet duct, the direction of the air flowing through the blades is not parallel to the engine axis. This sideslip angle results in so-called "IP" (one-per-rev or 1 / rev in English) forces which cause a vibratory response of the propeller blades on the "IN" engine order. Similarly, these "IP" forces can also appear during the climb or approach phases of the aircraft because the air flows through the blades with an angle of incidence. These vibratory excitations at high rotational speeds generate very significant stress cycling over the entire blade. In particular, the part of the blade root located between the hub and the vein, also called the "stilt", is a loaded and critical area due to its function of retaining the blade.

[0010] The present invention thus aims to propose a blade whose root is capable of holding the “IP” loads while limiting the mass of the blade as much as possible. Summary of the invention

[0011] The invention proposes a variable-pitch blade for an aircraft turbomachine propeller, this blade comprising a blade connected by a stilt to a root which is centered on a blade pitch axis, the blade being made of composite material from at least one metal body and a fiber preform obtained by three-dimensional fiber weaving and embedded in a polymer matrix which ensures the solidification of the preform with the metal body, the metal body forming at least the root and the stilt, and the fiber preform forming at least the blade which comprises a lower surface and an upper surface connected to each other by leading and trailing edges. of the blade, characterized in that the metal body also forms a first part of a spar which extends inside the blade along the pitch axis, the spar comprising a second part which is formed by the preform and which extends inside the blade along the pitch axis, the second part of the spar having a longitudinal end located on the root side which is engaged in a cavity of the first part of the spar.

[0012] The proposed solution consists of producing a blade made of 3D woven composite and a metal root. The particularity of this concept lies in the fact that the root and the blade stilt are made of metal material under the aerodynamic vein. Furthermore, another particularity lies in the constitution of the spar located inside the blade. The retention of the composite blade by the metal body is achieved inside the blade, by engagement of a part of the preform in a part of the metal body, and not by wedge effect on the outside of the root. This embodiment makes it possible to propose an alternative mode of retention of the composite blade by the metal root. This mode of retention reveals a part of the composite blade which plays the role of spar because it transfers the forces to the metal root.Therefore, the composite skins of the preform, close to the aerodynamic surfaces (intrados and extrados) of the blade, are less structural since they only have to reconstitute the aerodynamic profile in areas less loaded in terms of pressure.

[0013] The blade spar according to the invention thus comprises two parts and in particular two materials, unlike the prior art. A first metal part is formed by the body and is formed in a single piece with the root and Péchasse or is integral with the root and Péchasse. A second composite part is formed by the preform and is formed in a single piece with the rest of the preform or is integral with the rest of the preform. The assembly (body and preform) is further made integral thanks to the polymer matrix, for example by an RTM process or equivalent.

[0014] The blade according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another:

[0015] - the preform comprises at least one delinking of its fibers making it possible to define:

[0016] + an upper portion of the blade in which the fibers are secured to each other others over the entire thickness of the blade,

[0017] + a lower portion of the blade which is connected to the upper portion and which comprises two superimposed skins located respectively on the intrados and extrados sides of the blade, the fibers of each of the skins being integral with each other over the entire thickness of this skin, and

[0018] + the second part of the spar which is inserted between the two skins of the portion lower and which includes a longitudinal end opposite the foot which is connected to the upper portion,

[0019] the first part of the spar being inserted between the two skins; - the blade is further made from at least one block of foam which is located inside the blade; - a first block of foam is inserted between the skins, between the second part of the spar and the leading edge of the blade, and a second block of foam is inserted between the skins, between the second part of the spar and the trailing edge of the blade; - the first part of the spar has a dimension measured along a chord of the blade, which represents 80 and 120% of a dimension of the second part of the spar measured in the same way; - the first part of the spar comprises two wings, which are located respectively on the intrados and extrados sides of the blade, and which define between them said cavity which opens in the direction of the setting axis on the side of said second part of the spar to form an opening for receiving this second part; - the cavity opens at its two opposite ends located respectively on the side of the leading edge and the trailing edge of the blade; - the first part of the spar comprises two partitions which are located respectively on the side of the leading edge and the trailing edge of the blade, these partitions extending between the wings and connecting them together so as to close the two opposite ends of the cavity located respectively on the side of the leading edge and the trailing edge of the blade; - the receiving opening is delimited by two longitudinal edges of the wings, which are tapered; - the wings have:

[0020] + constant thicknesses over at least 50, or even 80%, of their height along said timing shaft, or

[0021] + thicknesses which vary along said wedging axis and which are for example maximum on the foot side or at mid-height of the wings;

[0022] - the wings have:

[0023] + constant thicknesses over at least 50, or even 80%, of their length along of a blade chord, or

[0024] + thicknesses which vary along a chord of the blade and which are for example maximum in the middle of the wings;

[0025] - the wings:

[0026] + are rectilinear and parallel, or

[0027] + are curved with concavities oriented towards each other,

[0028] + have first bosses oriented towards each other and second bosses oriented respectively towards the intrados and extrados sides of the blade;

[0029] - the first part of the spar further comprises at least one dividing wall of said cavity, this wall extending between the wings and at a distance from the wings, or extending from one wing to the other wing while being connected to these wings;

[0030] - the wall has a height along the wedging axis, which represents between 30 and 60% of a height of the wings along this axis;

[0031] - the wall is connected to said partitions;

[0032] - the metal body is formed:

[0033] + in one piece,

[0034] + at least two pieces, including a first piece comprising the foot, Péchasse and one of the wings, and a second piece comprising the other of the wings;

[0035] - the second part of the spar comprises at least one delinking of its fibers on at least at least a portion of its length, the first portion of the spar comprising at least one projection engaged in the second portion of the spar at the level of this disconnection;

[0036] - the second part of the spar is connected to the skins by fiber sails.

[0037] The present invention also relates to a turbomachine, in particular for an aircraft, in particular for an aircraft, comprising a propeller comprising at least one blade as described above.

[0038] The present invention finally relates to a method of manufacturing a blade as described above, in which it comprises the steps of:

[0039] a) three-dimensional weaving of fibers to form the preform, and unbinding of a portion of the preform to form the second portion of the spar,

[0040] b) compaction of the second part of the spar,

[0041] c) engagement of the second part of the spar in the cavity of the first part of the spar,

[0042] d) compaction of the assembly formed by the preform and the body,

[0043] e) RTM type consolidation of the assembly in a mold, comprising for example impregnation of the preform with a resin in the mold. Brief description of the figures

[0044] Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

[0045] [Fig-1] [Fig.l] is a schematic perspective view of a pitched blade variable for an aircraft turbomachine propeller,

[0046] [Fig.2] [Fig.2] is an enlarged view of part of [Fig.l] and shows the foot of dawn,

[0047] [Fig.3] [Fig.3] is a schematic axial sectional view of an angular setting system for a variable-pitch blade,

[0048] [Fig.4] [Fig.4] is a schematic sectional view of a blade according to a first embodiment of the invention,

[0049] [Fig.5] [Fig.5] is a partial schematic sectional view along line VV of [Fig.4],

[0050] [Fig.6] [Fig.6] is a schematic sectional view along line VI-VI of [Fig.4] or 5,

[0051] [Fig.7] [Fig.7] is a schematic view similar to that of [Fig.6] and illustrating a variant of realization,

[0052] [Fig.8] [Fig.8] is a schematic view similar to that of [Fig.6] and illustrating another variant embodiment,

[0053] [Fig.9] [Fig.9] is a schematic view similar to that of [Fig.6] and illustrating another variant of realization,

[0054] [Fig. 10] [Fig. 10] is a schematic view similar to that of [Fig.5] and illustrating another variant embodiment,

[0055] [Fig. 11] [Fig. 11] is a schematic view similar to that of [Fig.5] and illustrating another variant embodiment,

[0056] [Fig. 12] [Fig. 12] is a schematic sectional view of a blade according to another embodiment of the invention,

[0057] [Fig. 13] [Fig. 13] is a schematic sectional view along line XIII-XIII of [Fig.12],

[0058] [Fig. 14] [Fig. 14] is a partial schematic sectional view along line XIV-XIV of [Fig. 12],

[0059] [Fig. 15] [Fig. 15] is a schematic view similar to that of [Fig. 13] and illustrating another alternative embodiment,

[0060] [Fig. 16] [Fig. 16] is a schematic sectional view of a blade according to another embodiment of the invention,

[0061] [Fig. 17] [Fig. 17] is a schematic sectional view along line XVII-XVII of [Fig.16],

[0062] [Fig. 18] [Fig. 18] is a schematic view similar to that of [Fig. 17] and illustrating another alternative embodiment,

[0063] [Fig. 19] [Fig. 19] is a schematic view similar to that of [Fig. 17] and illustrating another variant embodiment,

[0064] [Fig.20] [Fig.20] is a schematic sectional view of a blade according to another embodiment of the invention, and

[0065] [Fig.21] [Fig.21] is a schematic view similar to that of [Fig.5] and illustrating another variant of realization. Detailed description of the invention

[0066] [Fig.l] shows a variable-pitch blade 10 for a propeller of an aircraft turbomachine, this propeller being shrouded or unshrouded.

[0067] The blade 10 comprises a blade 12 connected to a foot 14.

[0068] The blade 12 has an aerodynamic profile and comprises a lower surface 12a and an upper surface 12b which are connected by an upstream leading edge 12c and by a downstream trailing edge 12d, the terms upstream and downstream referring to the flow of gases around the blade in operation.

[0069] The blade 12 has an upper end which is free, called the apex, and a lower end which is connected to the root 14.

[0070] In the example shown, the blade 10 is made of composite material by an injection process called the RTM process (acronym for Resin Transfer Molding). This process consists of preparing a fiber preform 18 by three-dimensional weaving and then placing this preform in a mold and injecting a polymerizable resin such as an epoxy resin, which will impregnate the preform. After polymerization and hardening of the blade 12, its leading edge 12c is generally reinforced by a metal shield 20 added and fixed, for example by gluing.

[0071] The blade 10 here comprises a spar 22 which comprises a part forming a core of the blade 12 and which is intended to be inserted into the preform 18 before the injection of resin, and a part which extends on the side opposite the top of the blade 12 to form a part of the root 14, called body 24.

[0072] The spar 22 is generally made of an epoxy organic matrix composite material reinforced with 3D woven carbon fibers with the warp direction predominantly oriented radially and the weft predominantly oriented along the chord of the blade at the aerodynamic vein height. However, the spar can also be a more mechanically advantageous assembly of different organic matrix composite materials (thermosetting, thermoplastic or elastomer) reinforced with long fibers (carbon, glass, aramid, polypropylene) in several fiber arrangements (woven, braided, knitted, unidirectional).

[0073] Although not shown, the blade 12 may be hollow or solid and includes an internal cavity filled with a foam or honeycomb type filler material. This filler material is installed around the spar 22 and is covered with a skin of organic matrix composite material to increase the impact resistance of the blade.

[0074] The shield 20 may be titanium or a titanium alloy, stainless steel, steel, aluminum, nickel, etc. The intrados 12a or even the extrados 12b of the blade 12 may be covered with a poly- film urethane for erosion protection.

[0075] A denotes the axis of elongation of the blade 10 and of the blade 12 and in particular the setting axis of the blade 10, that is to say the axis around which the angular position of the blade is adjusted. It is generally also a radial axis which therefore extends along a radius relative to the axis of rotation of the propeller equipped with this blade.

[0076] The body 24 of the foot 14 has a particular shape better visible in [Fig.2].

[0077] The body 24 essentially comprises three parts, namely:

[0078] - a free end 28 located on the side opposite the blade 12,

[0079] - a stilt 30 located on the side of the blade 12, and

[0080] - a bulb 32 located between the free end 28 and Péchasse 30.

[0081] The free end 28 has a generally parallelepiped shape in the example shown. This end 28 is preferably off-center or offset relative to the axis A to provide keying or indexing.

[0082] The stilt 30 may have a relatively complex shape and may be considered as including:

[0083] - two lateral flanks 30a, 30b, located respectively on the side of the intrados 12a and the extrados 12b of the blade 12, which converge towards each other along the axis A and towards the top of the blade 12, and

[0084] - two edges, respectively upstream 30c and downstream 30d, which on the contrary diverge from one another on the other along the axis A and towards the top of the blade 12.

[0085] The bulb 32 has a generally swollen or domed shape, this swollenness or doming extending all around the axis A.

[0086] The bulb 32 has two peripheral bearing surfaces, respectively lower 32a and upper 32b, which extend around the axis A. In the example shown, due to the shape of the bulb, the lower bearing surface 32a is oriented downwards (i.e. on the side opposite the blade 12) and radially outwards relative to the axis A, and the upper bearing surface 32b is oriented upwards (i.e. on the side of the blade 12) and radially outwards relative to the axis A.

[0087] [Fig. 3] shows an example of a system 34 for angular setting of the blade 10. The system 34 essentially comprises a bowl 36, a ring 38, stops 40 and a nut 42, and has been described in detail in the prior application WO-A1-2023 / 031522.

[0088] The present invention proposes a new design of variable-pitch blade 10 for an aircraft turbomachine propeller, a first embodiment of which is illustrated in FIGS. 4 to 6.

[0089] This blade 10 comprises a blade 12 connected by a stilt 30 to a foot 14 which is centered on a blade setting axis A. The blade 10 is made of composite material from at least one metal body 50 and a fiber preform 52 obtained by weaving fibers in three dimensions and embedded in a polymer matrix which ensures the securing of the preform 52 with the metal body 50. The metal body 50 forms at least the root 14 and the stilt 30 of the blade 10. This body 50 can be formed in a single piece. The fibrous preform 52 forms at least the blade 12.

[0090] The particularity of the invention comes from the fact that the metal body 50 also forms a first part 54a of a spar 54 which extends inside the blade 12 along the pitch axis A, the spar 54 comprising a second part 54b which is formed by the preform 52 and which extends inside the blade 12 along the pitch axis A. Furthermore, the second part 54b of the spar 54 has a longitudinal end 54b 1 located on the side of the root 14 which is engaged in a cavity 56 of the first part 54a of the spar 54.

[0091] Figures 4 and following illustrate several variant embodiments of this blade 10. In these figures, the orthonormal reference frame XYZ comprises an axis X which is parallel to an axis of rotation of this blade and of the propeller carrying this blade (and which extends for example along a chord of the blade 10), an axis Z which extends parallel to the setting axis A, and an axis Y which is transverse and perpendicular to the axes X and Z.

[0092] The common elements of these blades 10 bear the same references and use references already used in the above insofar as these elements are common to the blade 10 of FIGS. 1 to 3 and have already been described in the above.

[0093] Advantageously, the preform 52 comprises at least one delinking of its fibers making it possible to define:

[0094] - an upper portion 52a of the blade 12 in which the fibers are secured to the from each other over the entire thickness of the blade 12,

[0095] - a lower portion 52b of the blade which is connected to the upper portion 52a and which comprises two superimposed skins 52b 1, 52b2 located respectively on the side of the intrados 12a and the extrados 12b of the blade 12, the fibers of each of the skins 52bl, 52b2 being integral with each other over an entire thickness E0 of this skin ( [Fig.5]), and

[0096] - the second part 54b of the spar 54 which is inserted between the two skins 52b 1, 52b2 of the lower portion 52b and which comprises a longitudinal end 54b2 opposite the foot 14 which is connected to the upper portion 52a,

[0097] the first part 54a of the spar 54 being interposed between the two skins 52b 1, 52b2.

[0098] Advantageously, the second part 54b of the spar 54 is stiffer along the axis A than the skins 52b 1, 52b 2 to avoid transferring force into the latter during bending of the blade 10 or centrifugal forces. On the other hand, the spar 54 may be less stiff than the skins 52b 1, 52b 2 along a chord of the blade 12. This may be obtained for example by varying the warp / weft ratio of the preform 52 or the nature of the fibers. As a reminder, in the preform 52, the wefts (or weft threads) of the preform 52 are “horizontal” (in the direction of a chord of the blade), and its warps (or warp threads) are “vertical” (in the direction of the axis A).

[0099] The separation between the skins 52b 1, 52b2 and the spar 54 outside the cavity 56 is therefore preferably done only by the material stiffness transition. There is then no inter-laminar interface between skins 52b 1, 52b2 and spar 54.

[0100] The blade 10 may further comprise at least one foam block 58, 60 which is located inside the blade 12.

[0101] A first block of foam 58 can be interposed between the skins 52bl, 52b2, between the second part 54b of the spar 54 and the leading edge 12c of the blade 12, and a second block of foam 60 can be interposed between the skins 52b1, 52b2, between the second part 54b of the spar 54 and the trailing edge 12d of the blade 12.

[0102] The first part 54a of the spar 54 may have a dimension L1 measured along a chord of the blade 14, which represents 80 and 120% of a dimension L2 of the second part 54b of the spar 54 measured in the same way ([Fig.4]).

[0103] [Fig.4] is a section passing through skeleton lines of the blade and midway between the intrados and extrados surfaces of the blade.

[0104] The first part 54a of the spar 54 may comprise two wings 62a, 62b, which are located respectively on the side of the intrados 12a and the extrados 12b of the blade 12, and which define between them the cavity 56 which opens in the direction of the setting axis A on the side of the second part 54b of the spar 54 to form an opening for receiving this second part 54b.

[0105] This receiving opening is delimited by two longitudinal edges 62al, 62bl of the wings 62a, 62b, which can be tapered as illustrated in the drawings.

[0106] In the embodiment of figures 4 to 6, the cavity 56 opens at its two opposite ends located respectively on the side of the leading edge 12c and the trailing edge 12d of the blade 12.

[0107] This configuration makes it possible to insert the second part 54b of the spar 54 by pinning into the first part 54a of the spar 54. In this case, the retention of the blade 12 by the root 14 operates in the following way: - recovery of the force Fy and the moments Mx and Mz by shape complementarity, - absorption of the forces Fx, Fz and the moments My by the adhesion interface between the parts 54a, 54b of the spar 54.

[0108] X being oriented along the engine axis, Z being oriented along the blade pitch change axis and Y being the vector product of X and Z.

[0109] The wings 62a, 62b have thicknesses E1 which vary along the wedging axis A and which are for example maximum on the side of the foot 14 ([Fig.5]).

[0110] The wings 62a, 62b have thicknesses E2 which vary along a chord of the blade 12. and which are for example maximal in the middle of the wings ([Fig.6]).

[0111] The wings 62a, 62b are substantially rectilinear and parallel. They have bosses oriented respectively towards the intrados 12a and the extrados 12b of the blade 12.

[0112] The embodiment variant of [Fig.7] differs from the previous embodiment in that the first part 54a of the spar 54 comprises two partitions 64a, 64b which are located respectively on the side of the leading edge 12c and the trailing edge 12d of the blade 12.

[0113] These partitions 64a, 64b extend between the wings 62a, 62b and connect them together so as to close the two opposite ends of the cavity 56 located respectively on the side of the leading edge 12c and the trailing edge 12d of the blade 12.

[0114] In this variant, the retention of the blade 12 by the foot 14 operates in the following way: - recovery of the forces Fx, Fy and the moments Mx, My, Mz by complementarity of shapes, - absorption of the force Fz by the adhesion interface between the parts of the spar.

[0115] The embodiment variant of [Fig.8] differs from the first embodiment in that the wings 62a, 62b are curved with concavities oriented towards each other. The wings 62a, 62b have constant thicknesses E2 over at least 50, or even 80%, of their length along a chord of the blade 12.

[0116] In this variant, the cavity 56 towards the leading and trailing edges 12c, 12d. However, the second part 54b of the spar 54 is inserted from above into the cavity 56. In this case, the retention of the blade 12 by the root 14 operates as follows: - recovery of the forces Fx, Fy and the moments Mx, My and Mz by complementarity of shapes, - absorption of the force Fz by the adhesion interface between the parts of the spar.

[0117] The embodiment variant of [Fig.9] differs from the first embodiment in that the wings 62a, 62b have first bosses oriented towards each other and second bosses oriented respectively towards the intrados and extrados sides of the blade. The wings 62a, 62b have thicknesses which vary along a chord of the blade and which are for example maximum in the middle of the wings.

[0118] The embodiment variant of [Fig. 10] differs from the first embodiment in that the wings 62a, 62b have thicknesses E1 which vary along the setting axis A and which are maximum at mid-height of the wings.

[0119] In this variant, the cavity 56 opens towards the leading and trailing edges 12c, 12d. This makes it possible to insert the second part 54b of the spar 54 by pinning (from the side) into the cavity 56, without necessarily requiring compaction of this part 54b. In this case, the retention of the blade 12 by the foot 14 works as follows: - absorption of the forces Fy, Fz and the moments Mx, My, Mz by complementarity of shape. - absorption of the forces Fx by the adhesion interface between the parts of the spar.

[0120] The embodiment variant of [Fig.l 1] differs from the first embodiment in that the wings 62a, 62b have constant thicknesses over at least 50, or even 80%, of their height along the wedging axis.

[0121] The variant embodiments of figures 12 to 17 differ from the first embodiment in particular in that the second part 54b of the spar 54 comprises at least one delinking of its fibers over at least part of its length.

[0122] Figures 12 to 14 illustrate another alternative embodiment which differs from the first embodiment in that the first part 54a of the spar 54 further comprises at least one wall 66 dividing the cavity 56.

[0123] This wall 66 extends between the wings 62a, 62b and at a distance from the wings, substantially parallel to these wings.

[0124] The wall 66 is inserted into a detachment of the second part 54b of the spar 54.

[0125] The wall 66 has a height H1 along the wedging axis A, which represents between 30 and 60% of a height H2 of the wings 62a, 62b along this axis A.

[0126] This wall 66 has a dimension L3 measured along a chord of the blade 14, which represents 80 and 120% of the dimension LL. In other words, the wings 62a, 62b and the wall 66 can have the same dimension measured in this way.

[0127] The wall 66 may have a thickness E3 which varies along the wedging axis A and which is for example maximum on the side of the foot 14.

[0128] The wall 66 may have a constant thickness E4 along a chord of the blade.

[0129] In this variant, the cavity 56 opens towards the leading and trailing edges. 12c, 12d. This allows the second part 54b of the spar 54 to be inserted by pinning into the cavity 56 of the first part 54a. However, since the second part 54b has a constant thickness along the wedging axis A before introduction into the cavity 56, it can also be inserted from above. The retention of the blade 12 by the root 14 works as follows: - recovery of the forces Fy, Fz and the moments Mx, My, Mz by shape complementarity. - absorption of the Fx forces by the adhesion interface between the parts of the spar because the thickness is constant in the chord direction.

[0130] The embodiment variant of [Fig. 15] differs from the previous embodiment in that the first part 54a of the spar 54 comprises two partitions 64a, 64b which are located respectively on the side of the leading edge 12c and the trailing edge 12d of the blade 12.

[0131] These partitions 64a, 64b which extend between the wings 62a, 62b and connect them together, are also connected to the wall 66, and close the two opposite ends of the cavity 56 located respectively on the side of the leading edge 12c and the trailing edge 12d of the blade 12.

[0132] In this variant, the second part 54b of the preform 54 can be inserted through the top of the cavity 56, it is therefore possible to have a non-opening cavity on the side of the leading and trailing edges 12c, 12d. The retention of the blade 12 by the root 12 operates in the following way:

[0133] - recovery of the forces Fx, Fy, Fz and the moments Mx, My, Mz by complementarity of shape.

[0134] Figures 16 and 17 illustrate another alternative embodiment which differs from the first embodiment in that the first part 54a of the spar 54 further comprises at least one wall 68 dividing the cavity 56.

[0135] This wall 68 extends from one wing 62a to the other wing 62b while being connected to these wings 62a, 62b.

[0136] The wall 68 is inserted into a detachment of the second part 54b of the spar 54.

[0137] The wall 68 has a height H1 along the wedging axis A, which represents between 30 and 60% of a height H2 of the wings 62a, 62b along this axis A.

[0138] The wall 68 may have a thickness E3 which varies along the wedging axis A and which is for example maximum on the side of the foot 14.

[0139] The wall 66 may have a constant thickness E4 between the intrados and the extrados of the blade 12.

[0140] The first part 54a of the spar 54 further comprises two partitions 64a, 64b which are located respectively on the side of the leading edge 12c and the trailing edge 12d of the blade 12.

[0141] These partitions 64a, 64b extend between the wings 62a, 62b and connect them together to close the two opposite ends of the cavity 56 located respectively on the side of the leading edge 12c and the trailing edge 12d of the blade 12. The partitions 64a, 64b and the wall 68 are substantially parallel.

[0142] The variant embodiments of figures 18 and 19 differ from the first embodiment in particular in that the second part 54b of the spar 54 comprises at least one delinking 70 of its fibers over at least part of its length.

[0143] The first part 54a of the spar 54 comprises at least one projection 72 engaged in the second part 54b of the spar 52 at the level of this separation 70. In the examples shown, the second part 54b of the spar 54 comprises a first separation 70 located on the side of the leading edge of the blade 12 and in which is engaged a first projection 72 of the first part 54a of the spar 54, and a second separation 70 located on the side of the trailing edge of the blade 12 and in which is engaged a second projection 72 of the first part 54a of the spar 54.

[0144] The projections 72 are substantially pointed.

[0145] In these figures 18, 19, it can be seen that the first part 54b of the preform 54 has a general H or X shape in cross section. The cavity 56 also has a similar general shape in cross section.

[0146] Furthermore, in the embodiment variant of [Fig. 18], the second part 54b of the spar 54 is connected to the skins 52b 1, 52b 2 by fiber webs 74. These fiber webs 74 can extend over all or part of the length of the second part 54b, along the wedging axis A.

[0147] The embodiment variant of [Fig. 20] differs for example from the variant of figures 16 and 17 in that the dividing wall 68 is replaced by a bar 76. The bar 76 extends from one wing 62a to the other wing 62b while being connected to these wings 62a, 62b.

[0148] The bar 76 is located at a distance from the bottom of the cavity 56 and may have a circular or oval shape in section as illustrated in the drawing.

[0149] The bar 76 passes through an arrangement of complementary shape to the end 54bl of the second part 54b of the spar 54, this arrangement being for example an orifice.

[0150] The embodiment variant of [Fig.21] differs from the variant of figures 16 and 17 in that the body 50 is formed of at least two parts 50a, 50b.

[0151] A first part 50a of the body 50 comprises the foot 14, Péchasse 30, one of the wings 62a, or even also the wall 66.

[0152] A second part 50b of the body 50 comprises the other wing 62b and is fixed to the first part by any appropriate means or technique such as for example by welding.

[0153] In still other variants not shown: - a layer of glue may be provided at the interface between the parts 54a, 54b of the spar to reinforce the adhesion properties if those provided by the polymer matrix are not sufficient, - the blade may be without foam and comprises skins 52b 1, 52b2 of greater thickness occupying the volume of the foams, - a space or clearance could be provided between the end 54b 1 of the spar 54 and the bottom of the cavity 56.

[0154] The present invention also relates to a method of manufacturing the blade 10 according to the invention, this method comprising the following steps:

[0155] a) three-dimensional weaving of fibers to form the preform 52, and uncoupling of a portion of the preform 52 to form the second portion 54b of the spar 54,

[0156] b) compaction of the second part 54b of the spar 54,

[0157] c) engagement of the second part 54b of the spar 54 in the cavity 56 of the first part 54a of the spar 54,

[0158] d) compaction of the assembly formed by the preform 52 and the body 50,

[0159] e) RTM type consolidation of the assembly in a mold.

[0160] RTM (Resin Transfer Molding) consolidation is well known to those skilled in the art. profession and will not be described in detail.

[0161] The method may further comprise one or more of the following steps: water jet cutting of contours of the preform, insertion of the foam(s) 58, 60 between the skins of the preform 52, bonding of a shield 20 on the leading edge 12c, machining, coating of the intrados 12a and the extrados 12b with a layer of PU (polyurethane), bonding of a heating mat and / or anti-wear strips on the foot 14, etc.

[0162] The present invention has numerous advantages, including:

[0163] - the foot of the dawn and Péchasse are only made of metallic material,

[0164] - the retention of the composite blade by the metal foot is carried out in the cavity of the foot and not by wedge effect on the outside of the foot,

[0165] - part of the blade plays the role of a spar because it transmits the forces towards the metal foot,

[0166] - the skins of the preform are less structural since they must only reconstruct the aerodynamic profile in areas less loaded in terms of pressure,

[0167] - etc.

Claims

Claims

1. Variable-pitch blade (10) for an aircraft turbomachine propeller, this blade (10) comprising a blade (12) connected by a stilt (30) to a root (14) which is centered on a blade-pitch axis (A), the blade (10) being made of composite material from at least one metal body (50) and a fiber preform (52) obtained by three-dimensional fiber weaving and embedded in a polymer matrix which ensures the attachment of the preform (52) to the metal body (50), the metal body (50) forming at least the root (14) and stilt (30), and the fiber preform (52) forming at least the blade (12) which comprises a lower surface (12a) and an upper surface (12b) connected to each other by leading (12c) and trailing (12d) edges of the blade (12), characterized in that the metal body (50) also forms a first part (54a) of a spar (54) which extends inside the blade (12) along the pitch axis (A),the spar (54) comprising a second part (54b) which is formed by the preform (52) and which extends inside the blade (12) along the setting axis (A), the second part (54b) of the spar (54) having a longitudinal end (54b 1) located on the side of the root (14) which is engaged in a cavity (56) of the first part (54a) of the spar (54).,

2. Blade (10) according to claim 1, in which the preform (52) comprises at least one delinking of its fibers making it possible to define: - an upper portion (52a) of the blade (12) in which the fibers are integral with each other over an entire thickness of the blade, - a lower portion (52b) of the blade (12) which is connected to the upper portion (52a) and which comprises two superimposed skins (52b1, 52b2) located respectively on the side of the intrados (12a) and the extrados (12b) of the blade (12), the fibers of each of the skins (52b1, 52b2) being integral with each other over an entire thickness of this skin (52b1, 52b2), and - the second part (54b) of the spar (54) which is interposed between the two skins (52b1, 52b2) 52b2) of the lower portion (52b) and which comprises a longitudinal end (54bl) opposite the foot (14) which is connected to the upper portion (52a),the first part (54a) of the spar (54) being inserted between the two skins (52b 1, 52b2).,

3. A blade (10) according to any preceding claim, wherein it is further made from at least one block of foam (58, 60) which is located inside the blade (12).

4. Blade (10) according to claim 3 as dependent on claim 2, in which a first block of foam (58) is interposed between the skins (52b 1, 52b2), between the second part (54b) of the spar (54) and the leading edge (12c) of the blade (12), and a second block of foam (60) is interposed between the skins (52b 1, 52b2), between the second part (54b) of the spar (54) and the trailing edge (12d) of the blade (12).

5. A blade (10) according to any preceding claim, wherein the first portion (54a) of the spar (54) has a dimension (L1) measured along a chord of the blade (12), which represents 80 and 120% of a dimension (L2) of the second portion (54b) of the spar (54) measured in the same way.

6. Blade (10) according to one of the preceding claims, in which the first part (54a) of the spar (54) comprises two wings (62a, 62b), which are located respectively on the side of the intrados (12a) and the extrados (12b) of the blade (12), and which define between them said cavity (56) which opens in the direction of the setting axis (A) on the side of said second part (54b) of the spar (54) to form an opening for receiving this second part (54b).

7. Blade (10) according to claim 6, in which the cavity (56) opens at its two opposite ends located respectively on the side of the leading edge (12c) and the trailing edge (12d) of the blade (12).

8. Blade (10) according to claim 6, in which the first part (54a) of the spar (54) comprises two partitions (64a, 64b) which are located respectively on the side of the leading edge (12c) and the trailing edge (12d) of the blade (12), these partitions (64a, 64b) extending between the wings (62a, 62b) and connecting them together so as to close the two opposite ends of the cavity (56) located respectively on the side of the leading edge (12c) and the trailing edge (12d) of the blade (12).

9. Blade (10) according to one of claims 6 to 8, in which the receiving opening is delimited by two longitudinal edges (62a 1, 62b 1) of the wings (62a, 62b), which are tapered.

10. Blade (10) according to one of claims 6 to 9, in which the wings (62a, 62b) have: - constant thicknesses (El) over at least 50, or even 80%, of their height along said setting axis (A), or - thicknesses (El) which vary along said setting axis (A) and which are for example maximum on the foot side (14) or at mid-height of the wings.

11. Blade (10) according to one of claims 6 to 10, in which the wings (62a, 62b) have: - constant thicknesses (E2) over at least 50, or even 80%, of their length along a chord of the blade (12), or - thicknesses (E2) which vary along a chord of the blade (12) and which are for example maximum in the middle of the wings (62a, 62b).

12. Blade (10) according to one of claims 6 to 11, in which the wings (62a, 62b): - are rectilinear and parallel, or - are curved with concavities oriented towards each other, - have first bosses oriented towards each other and second bosses oriented respectively towards the intrados (12a) and extrados (12b) sides of the blade (12).

13. Blade (10) according to one of claims 6 to 12, in which the first part (54a) of the spar (54) further comprises at least one wall (66, 68) dividing said cavity (56), this wall (66, 68) extending between the wings (62a, 62b) and at a distance from the wings, or extending from one wing to the other wing while being connected to these wings.

14. Blade (10) according to claim 13, in which the wall (66, 68) has a height (H1) along the setting axis (A), which represents between 30 and 60% of a height (H2) of the wings (62a, 62b) along this axis (A).

15. A blade (10) according to claim 13 or 14, dependent on claim 8, wherein the wall (66, 68) is connected to said partitions (64a, 64b).

16. Blade (10) according to one of the preceding claims, in which the metal body (50) is formed: - from a single piece, - from at least two pieces (50a, 50b), including a first piece (50a) comprising the foot (14), Péchasse (30) and one of the wings (62a), and a second piece (50b) comprising the other of the wings (62b).

17. Blade (10) according to one of the preceding claims, in which the second part (54b) of the spar (54) comprises at least one detachment (70) of its fibers over at least part of its length, the first part (54a) of the spar (54) comprising at least one projection (72) engaged in the second part (54b) of the spar at the level of this detachment (70).

18. Blade (10) according to one of the preceding claims, in which the second part (54b) of the spar (54) is connected to the skins (52b 1, 52b2) by fiber webs (74).

19. Turbomachine, in particular for an aircraft, comprising a propeller comprising at least one blade (10) according to one of the preceding claims.

20. A method of manufacturing a blade (10) according to one of claims 1 to 18, wherein it comprises the steps of: a) weaving fibers in three dimensions to form the preform (52), and decoupling a portion of the preform (52) to form the second portion (54b) of the spar (54), b) compacting the second portion (54b) of the spar (54), c) engaging the second portion (54b) of the spar (54) in the cavity (56) of the first portion (54a) of the spar (54), d) compacting the assembly formed by the preform (52) and the body (50), e) RTM-type consolidation of the assembly in a mold.

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