One-piece turbine engine blade

Abstract

The invention relates to a turbine engine blade (7) comprising: - a sleeve (13) comprising a fastening portion (14) configured to be connected to a variable pitch mechanism of a turbine engine, wherein a through-cavity (17) is formed in the fastening portion (14) of the sleeve (13), the cavity (17) being bounded by an inner wall of the sleeve (13); - a fibrous structure (20) obtained via three-dimensional weaving of strands, the fibrous structure (20) comprising: - a blade root (22) comprising an attachment portion (23) configured to be inserted into the cavity (17) of the fastening portion (14) of the sleeve (13); - an airfoil blade (12) connected to the blade root (22); - an insert (24) configured to be inserted into the cavity (17) of the fastening portion (14) of the sleeve (13) and to press the blade root (22) against the inner wall (18) of the sleeve (13).

Description

[0001] TITLE: MONOBLOCK TURBOMACHINE BLADE

[0002] FIELD OF THE INVENTION

[0003] The invention relates generally to the field of turbomachines, and in particular to turbomachine blades.

[0004] The invention relates more particularly, but not exclusively, to a blade intended to be used in an unducted fan rotor of an aircraft engine.

[0005] TECHNOLOGICAL BACKGROUND

[0006] The advantage of unducted fan engines is that the fan diameter is not limited by the presence of a shroud, so it is possible to design an engine with a high bypass ratio (known as "By Pass Ratio" or BPR), and therefore reduced fuel consumption. Thus, in this type of engine, the fan blades can have a large span.

[0007] In addition, these engines generally include a mechanism for modifying the pitch angle of the blades in order to adapt the thrust generated by the fan according to the different phases of flight.

[0008] However, the design of such blades requires taking into account opposing constraints.

[0009] On the one hand, the sizing of these blades must allow for optimal aerodynamic performance, in particular maximizing efficiency and providing thrust while minimizing losses. Improving the aerodynamic performance of the fan tends towards an increase in the bypass ratio, which results in an increase in the external diameter, and therefore the span of these blades.

[0010] On the other hand, it is also necessary to guarantee resistance to the mechanical constraints that can be exerted on these blades while limiting their acoustic signature.

[0011] Furthermore, on unducted fan designs, engine starting is generally carried out with a very open timing. Indeed, a very open timing allows power to be consumed by torque, which ensures machine safety by guaranteeing low fan speeds.

[0012] However, with a very open pitch, the blades undergo a turbulent, completely detached aerodynamic flow, which generates a broadband vibration excitation. In particular, on blades with a wide chord and large span, the bending force is intense, although the engine speed is not maximum.

[0013] In normal operation, namely during the ground and flight phases, the pitch is modified so that the pitch angle is more closed. The aerodynamic flow is then perfectly healthy, in particular reattached to the aerodynamic profile. The broadband stresses disappear since the rotation speed is higher, and the bending force is controlled. However, since the engine is unducted, the incidence seen by the different fan blades depending on their angular position varies according to the angle of attack of the aircraft, creating a cyclic bending moment (commonly called 1 P moment) on the blades. This cyclic bending moment then generates strong bending stresses on the blades in addition to the centrifugal forces due to their rotation.

[0014] These blades can be made of metallic material. While metallic blades have good mechanical strength, they have the disadvantage of being relatively heavy.

[0015] Manufacturing blades from composite material is an interesting solution for reducing the weight of the blades. However, blades made from composite material can be fragile due to the intense aerodynamic forces to which they are subjected. These aerodynamic forces can therefore damage the blades and / or the hub in the interface zone between these blades and the fan rotor hub, at the blade root.

[0016] To overcome these drawbacks, various solutions exist in the prior art. Most use reinforcing elements, particularly at the blade root, and add various structural elements to enable, for example, the blade to be fixed to the setting mechanism. Patent documents WO2022 / 018353 and WO2022 / 208002 describe the addition of reinforcing elements and structural elements, particularly at the blade roots.

[0017] However, these solutions have the disadvantage of having to manufacture several elements in materials that may be different and having to assemble them using fixing means. Such blades can therefore take a relatively long time to manufacture.

[0018] BRIEF DESCRIPTION OF THE INVENTION

[0019] One of the aims of the invention is therefore to propose a blade suitable for use with a variable pitch mechanism and in an “Open Rotor” type environment while being capable of withstanding intense aerodynamic forces, under the constraint of limited bulk and minimal mass, the blade comprising a limited number of structural elements and being quick to manufacture.

[0020] Another object of the invention is to propose a blade comprising a composite material and suitable for use with a variable pitch mechanism and in an “Open Rotor” type environment which comprises a limited number of structural elements and which can be produced simply and quickly, without requiring a large number of operations.

[0021] For this purpose, according to a first aspect of the invention, there is proposed a blade for a turbomachine comprising:

[0022] - a sleeve, comprising a fixing part configured to be connected to a variable timing mechanism of a turbomachine, a through recess being formed in the fixing part of the sleeve, the recess being delimited by an internal wall of the sleeve having a length L;

[0023] - a fibrous structure obtained by three-dimensional weaving of strands, the fibrous structure comprising:

[0024] - a blade root comprising an attachment portion configured to be inserted into the recess of the attachment part,

[0025] - an aerodynamically profiled blade connected to the blade root;

[0026] - an insert, configured to be inserted into the recess of the attachment part of the sleeve and to press the blade root against the internal wall of the sleeve, so that the attachment portion is positioned directly in contact with the internal wall of the sleeve, and this, over at least 30% of the length L of the internal wall of the sleeve.

[0027] The blade is thus formed of a few elements which are assembled together to form a single-piece blade. Since the blade and the blade root are formed by the same fiber structure, there is no discontinuity between the blade and the blade root. Furthermore, the blade root is wedged between the insert and the sleeve and the fiber structure is thus firmly assembled with the blade root. In a known manner, it is possible to add an adhesive joint between the sleeve and the fiber structure to promote the transmission of forces between these elements.

[0028] The blade can thus withstand significant aerodynamic forces while having a limited mass and can therefore be used with a variable pitch mechanism and in an "Open Rotor" type environment. Furthermore, since the elements forming the blade are limited in number, the blade is quick to manufacture.

[0029] The inner wall of the sleeve has a length extending from a first opening of the sleeve to a second opening of the sleeve, the second opening being opposite the first opening. Preferably, the blade root, in particular the attachment portion of the blade root, is positioned directly in contact with the inner wall of the sleeve over at least 40% of the length L of the inner wall of the sleeve, more preferably over 60% of the length L, and may extend over the entire length of the inner wall of the sleeve.

[0030] According to particular embodiments of the invention which can be taken alone or in combination: the blade root further comprises a skirt extending around the attachment portion of the sleeve and the attachment part further comprises an annular flange, and an end face of the skirt of the blade root is configured to bear against the flange; the internal wall of the sleeve comprises a hollow portion causing the recess to widen in a radial direction and the attachment portion comprises an excess thickness configured to be housed in the hollow portion; the sleeve further comprises a one-piece connecting portion with the attachment part and in which the recess extends, the blade root being configured to be inserted into the connecting portion; the connecting portion of the sleeve extends between the attachment portion and the skirt of the blade root;the sleeve further comprises a stop extending from the inner wall, the insert being configured to press the blade root against the stop; the stop is formed by a reduction in the section of the recess in the connecting portion of the sleeve; a cross-section of the connecting portion of the sleeve is flattened in one direction; the fixing portion of the sleeve has an external surface having a shape of revolution in which at least one circular groove is formed, suitable for forming a raceway for at least one bearing;the fixing part of the sleeve has a shape of revolution and the connecting part of the sleeve comprises a first portion, connected to the fixing part, and a second portion connected to the first portion, the first portion having a shape of revolution of which a section decreases from the fixing part of the sleeve towards the second portion, the second portion having a reduced cross-section in a direction of space;and the sleeve is metallic. According to a second aspect, the invention provides a method for manufacturing a blade according to the first aspect, said method comprising the following steps: producing the fibrous structure comprising the attachment portion by three-dimensional weaving, inserting the attachment portion into the recess of the sleeve and against the internal wall, positioning the insert in the recess so as to block the attachment portion against the internal wall, and inserting the fibrous structure, the sleeve and the insert into a mold to obtain a preform with an aerodynamic profile.;

[0031] The method may further comprise a step of injecting a resin into the mold, after inserting the fiber structure, the sleeve and the insert into said mold, so as to obtain the blade according to the first aspect, said blade being in one piece.

[0032] The method may also include a step of positioning the blade root skirt on the connecting portion before inserting the fiber structure, the sleeve, and the insert.

[0033] Furthermore, the production of the fibrous structure may comprise the production of a first tab and a second tab, the first and second tabs each comprising two beveled lateral edges over at least part of their length and being intended to form together the attachment portion, and, when inserting the fibrous structure into the mold, the first and second tabs may be assembled by joining two by two the beveled lateral edges of the first tab with the beveled lateral edges of the second tab so as to form a cylindrical attachment portion.

[0034] According to a third aspect, the invention proposes a fan comprising at least one blade according to the first aspect or obtained according to the method of the second aspect.

[0035] According to a fourth aspect, the invention proposes a turbomachine comprising a fan according to the third aspect.

[0036] According to a fifth aspect, the invention proposes an aircraft comprising a fan according to the third aspect or a turbomachine according to the fourth aspect.

[0037] BRIEF DESCRIPTION OF THE FIGURES

[0038] Other characteristics and advantages of the invention will appear on reading the description which follows, given solely by way of example and made with reference to the appended drawings, in which: [Fig. 1] Figure 1 schematically represents an example of an engine including an unducted fan;

[0039] [Fig. 2] Figure 2 schematically represents a fan blade according to an embodiment of the invention assembled to a timing mechanism;

[0040] [Fig. 3] Figure 3 schematically represents a fan blade according to a first embodiment of the invention;

[0041] [Fig. 4a] Figure 4a schematically represents a sleeve according to a first embodiment of the invention in a perspective view;

[0042] [Fig. 4b] Figure 4b schematically represents the sleeve of Figure 4a in a profile view;

[0043] [Fig. 4c] Figure 4c schematically represents the sleeve of Figures 4a and 4b in which the attachment portion and the insert are inserted;

[0044] [Fig. 4d] Figure 4d schematically represents the sleeve / fastening portion / insert assembly of Figure 4c inserted into the wedging mechanism;

[0045] [Fig. 5a] Figure 5a schematically represents a fibrous structure according to one embodiment in partial and front view;

[0046] [Fig. 5b] Figure 5b schematically represents the fibrous structure of Figure 5a in a cross-sectional view;

[0047] [Fig. 5c] Figure 5c schematically represents the attachment portion of the fibrous structure of Figures 5a and 5b in a cross-sectional view;

[0048] [Fig. 6] Figure 6 schematically represents an insert according to one embodiment of the invention;

[0049] [Fig. 7a] Figure 7a schematically represents a sleeve according to a second embodiment of the invention in a perspective view;

[0050] [Fig. 7b] Figure 7b schematically represents the sleeve of Figure 7a in a profile view;

[0051] [Fig. 7c] Figure 7c schematically represents a fan blade according to a second embodiment of the invention;

[0052] [Fig. 8] Figure 8 schematically represents a method of manufacturing a blade according to an embodiment of the invention;

[0053] [Fig. 9a] Figure 9a shows the blade obtained according to the method of Figure 8 in front view; and

[0054] [Fig. 9b] Figure 9b shows the blade obtained according to the method of Figure 8 in profile view. DETAILED DESCRIPTION OF AN EXAMPLE OF EMBODIMENT

[0055] In Figure 1, the engine 1 shown is an “Open Rotor” type engine, in a configuration commonly referred to as “pusher” (i.e. the blower is placed at the rear of the power generator with an air inlet located on the side, on the right in Figure 1).

[0056] The engine comprises a nacelle 2 intended to be fixed to a fuselage of an aircraft, and an unducted fan 3. The fan 3 comprises two counter-rotating fan rotors 4 and 5. In other words, when the engine 1 is in operation, the rotors 4 and 5 are rotated relative to the nacelle 2 around the same axis of rotation X (which coincides with a main axis of the engine), in opposite directions.

[0057] In the example illustrated in Figure 1, the engine 1 is an “Open Rotor” type engine, in “pusher” configuration, with counter-rotating fan rotors. However, the invention is not limited to this configuration. The invention also applies to “Open Rotor” type engines, in “puller” configuration (i.e. the fan is placed upstream of the power generator with an air inlet located before, between or just behind the two fan rotors).

[0058] Furthermore, the invention also applies to engines having different architectures, such as an architecture comprising a fan rotor comprising moving blades and a fan stator comprising fixed blades, or a single fan rotor.

[0059] The invention is applicable to turboprop-type architectures (comprising a single fan rotor).

[0060] In Figure 1, each fan rotor 4, 5 comprises a hub 6 rotatably mounted relative to the nacelle 2 and a plurality of blades 7 according to one embodiment of the invention, said blades being fixed to the hub 6. The blades 7 extend substantially radially relative to the axis of rotation X of the hub.

[0061] As illustrated in Figure 2, the fan 3 further comprises an actuating mechanism 8 for collectively modifying the pitch angle of the rotor blades, in order to adapt the performance of the engine to the different flight phases. For this purpose, each blade 7 comprises a blade root 9 and an aerodynamically profiled blade 12. The blade root 9 is rotatably mounted relative to the hub 6 about a pitch axis Y. More precisely, the blade root 9 is rotatably mounted inside an attachment device 10 formed in the hub 6, by means of balls 11 or other rolling elements. The aerodynamically profiled blade 12 has a first end connected to the blade root 9 and a second end, opposite the first end. The aerodynamically profiled blade portion 12 is intended to extend into an air stream of the engine, when the engine is in operation, in order to generate lift.On the other hand, the blade root 9 is intended to extend outside the air stream.

[0062] According to a first embodiment described with reference to figures 3, 4a and 4b, the blade 7 comprises a sleeve 13 comprising a fixing part 14 configured to be connected to a variable setting mechanism of a turbomachine, in particular inside the attachment device 10. The sleeve 13 comprises a recess 17 delimited by an internal wall 18 of the sleeve 13.

[0063] With reference to Figures 3, 5a and 5b, the blade 7 also comprises a fibrous structure 20 obtained by three-dimensional weaving. The fibrous structure 20 comprises a blade root 22 comprising an attachment portion 23 configured to be inserted into the recess 17 formed by the attachment portion 14 of the sleeve 13.

[0064] The fibrous structure 20 also comprises a blade 21 with an aerodynamic profile connected to the blade root 22.

[0065] The blade 7 also comprises an insert 24 shown in FIG. 6 and which is configured to be inserted into the recess 17 of the fixing part 14 of the sleeve and to press the blade root 22 against the internal wall 18 of the sleeve 13.

[0066] The blade 7 is thus formed of a few elements which assemble with each other so as to form a single-piece blade. The blade 21 and the blade root 22 being formed by the same fibrous structure 20, there is no discontinuity between the blade 21 and the blade root 22. Furthermore, the blade root 22 is wedged between the insert 24 and the sleeve 13 and the fibrous structure 20 is thus firmly assembled with the blade root 9.

[0067] The blade 7 can thus withstand significant aerodynamic forces while having a limited mass and can thus be used with a variable pitch mechanism and in an “Open Rotor” type environment. Furthermore, since the elements forming the blade 7 are limited in number, the blade 7 is quick to manufacture.

[0068] With reference to Figure 5a, the blade root 22 further comprises a skirt 25 which extends around the attachment portion 23. The skirt 25 is formed by the same fibrous structure 20 as the blade 21 and the attachment portion 23. Thus, the attachment portion 23 on the one hand, and the skirt 25, on the other hand, are formed by the extension of the strands forming the blade 21. This continuity between the blade 21 and the attachment portion 23, and between the blade 21 and the skirt 25, allows the blade 7 to resist in an optimized manner the aerodynamic forces to which it is subjected.

[0069] The fibrous structure 20, and in particular the aerodynamically profiled blade 12, is suitable for being placed in an air flow when the engine is operating in order to generate lift.

[0070] As illustrated in Figure 5b, the fiber structure 20 comprises two skins 22', which are connected to each other and extend generally opposite each other. The skins 22' are shaped so as to define together a lower surface I, an upper surface E, a leading edge 15 and a trailing edge 15'. In a manner known per se, the leading edge 15 is configured to extend opposite the flow of gases entering the turbomachine. It corresponds to the front part of an aerodynamic profile which faces the air flow and which divides the air flow into a lower surface flow and an upper surface flow. The trailing edge 15' corresponds to the rear part of the aerodynamic profile, where the lower and upper surface flows meet.

[0071] The skins 22' of the aerodynamic profile structure are made of a composite material comprising the fibrous structure 20 densified by a matrix. They are therefore monolithic and are made in a single piece according to a non-limiting embodiment.

[0072] The matrix typically comprises an organic material (thermosetting, thermoplastic or elastomeric) or a carbon matrix. For example, the matrix may comprise a plastic material, typically a polymer, for example epoxy, bismaleimide or polyimide. The fibers of the fibrous structure 20 comprise at least one of the following materials: carbon, glass, aramid, polypropylene and / or ceramic. The matrix and the fibers of the composite materials.

[0073] The attachment portion 23 and the skirt 25 are formed by uncouplings in the three-dimensional weaving. Preferably, at least a portion of the strands forming the attachment portion 23 and / or the skirt 25 extend from a free end 28 of the blade 12 to a free end 23' of the attachment portion 23 and / or a free end 25' of the skirt 25.

[0074] In this way, the three-dimensional structure of the fibrous structure 20 extends into the sleeve 13 and optionally around the latter and this continuity contributes to the resistance of the blade to the aerodynamic forces to which it is subjected.

[0075] Concerning the formation of the attachment portion 23 and as illustrated in Figure 5c, each skin comprises a tab 60 (62) positioned opposite the free end 28, the tab 60 of one skin being intended to be assembled with the tab 62 of the other skin to form the cylindrical attachment portion 23. The tabs 60 and 62 are produced during flat weaving. The preform of the fibrous structure 20 is divided in two in the thickness by making unlinks. The independent flat tabs 60 and 62 are then obtained, each of which is connected to one of the skins 22' since there is continuity of the strands. This continuity of the strands allows the transfer of mechanical loads between the blade 21 and the blade root 22.

[0076] As described in more detail below, the flat tabs 60 and 62 are then shaped into a half-cylinder to form a cylindrical attachment portion 23.

[0077] Furthermore, each tab 60 (62) has a first lateral edge 60a (62a) and a second lateral edge 60b (62b) which are beveled over at least part of their length. As shown in FIG. 5c, the two tabs 60 and 62 are assembled by joining the beveled edges two by two so as to form the cylindrical attachment portion 23 having a relatively constant thickness over its entire circumference.

[0078] With reference to Figures 4c, 4b and 4c, the attachment portion 23 further comprises an excess thickness 23” which comes from a progressive thickening of the fibrous structure 20 forming said attachment portion 23, at its free end 23'. This excess thickness 23” is configured to be inserted into a hollow portion 18' of the internal wall 18. Thus, the portion 18' widens the recess 17 and the remainder of the part of the wall 18 narrows the recess 17. In this way, when the insert is positioned in the recess 17, any translation of the attachment portion 23 away from the free end 23' is prevented by the part of the wall 18 which narrows the recess 17 and forms a stop.

[0079] Indeed, when the fan is rotating, the blade 7 undergoes centrifugal forces oriented in a radial direction relative to the axis of rotation of the fan, which tend to separate the aerodynamically profiled blade 12 from the sleeve 13. The extra thickness 23” contributes to preventing the separation of the blade 12 and the sleeve 13. The blade 7 may also comprise one or two cavities, preferably two cavities 26, each allowing a shaping part 27 to be received. The cavities 26 are formed by delinkages in the weaving. Each shaping part 27 is formed from a rigid and lightweight material so as to reduce the mass of the blade 12 while allowing it to retain its aerodynamic shape.

[0080] The rigid material forming the shaping part(s) is preferably honeycombed, for example a foam, and formed for example from pre-machined polymethacrylimide (PMI). Alternatively, the rigid honeycombed material may be a pre-sealed aluminum honeycomb material.

[0081] The shaping part(s) 27 make it possible to give the desired thickness and shape to the aerodynamic profile blade 12 of the vane 7, while using a lighter material than other elements of the blade. However, according to a possible embodiment, the cavities can remain empty and not be filled with filling parts.

[0082] According to this first embodiment and with reference to figures 3, 4a to 4d, the fixing part 1 has a symmetry of revolution around the Y axis. Furthermore, the fixing part 14 comprises an external surface 30 having different reliefs.

[0083] The fixing part 14 comprises at its end through which the attachment portion 23 is inserted a first annular flange 29. This first annular flange 29 forms a stop against which an end face 25' of the skirt 25 of the blade root 22 is configured to come to bear.

[0084] The fixing part 14 also comprises a second annular flange 29' at its free end opposite the end through which the fibrous structure 20 is inserted.

[0085] The fixing part 14 also comprises a first circular groove 32 and a second circular groove 34 making it possible to form a raceway on at least one bearing, for example a ball bearing. The fixing part 14 thus allows the blade root 9 to be rotatably mounted inside the attachment device 10 formed in the hub 6.

[0086] The sleeve 13 is preferably metallic and monolithic.

[0087] As previously described, the sleeve 13 comprises an internal wall 18 which delimits the recess 17. In this first embodiment, the recess 17 forms a cylinder of constant diameter and which widens as it approaches the free end of the sleeve 13, forming a beveled internal edge. The wall 18 thus comprises a hollow portion 18' which widens the recess 17 in a radial direction. The excess thickness 23” of the attachment portion 23 is then inserted into the hollow portion 18' so as to prevent any translation of the attachment portion 23 away from the free end 23' when the insert 24 is positioned in the recess 17. The part of the wall 18 which has a constant diameter then forms a stop for the excess thickness 23”.

[0088] The free end of the sleeve forms a first opening 33 and the sleeve 13 further comprises a second opening 33' opposite the first opening 33. The internal wall 18 of the sleeve 13 thus has a length L going from the first opening 33 to the second opening 33'.

[0089] According to a possible embodiment variant, the hollow portion may have another shape and may be placed in another position along the wall 18.

[0090] Furthermore, according to another variant embodiment not shown, the wall 18 can thicken at its end opposite the free end so as to reduce the diameter of the recess 17 and form a stop making it possible to block the insert 24 and to wedge the attachment portion 23 against the wall 18 in an optimized manner.

[0091] Figure 4d shows the sleeve in which the attachment portion 23 and the insert 24 are inserted, the sleeve being arranged in the attachment device 10, the rolling elements 11 being arranged in the circular grooves 32 and 34.

[0092] In this embodiment, the attachment portion 23 is positioned directly in contact with the internal wall 18 of the sleeve 13, and this, over the entire length of the internal wall 18. However, according to a possible variant embodiment, the attachment portion may be in contact with only 20% of the length L, at least 40% of the length or at least 60% of the length.

[0093] Referring to Figure 6, the insert 24 comprises a cylindrical body 40 comprising a free end 41 and a locking end 42 opposite the free end 41. The locking end 42 is, in this embodiment, a rounded end. According to the alternative embodiment in which the sleeve 13 comprises a stop, the locking end 42 which is rounded allows the insert 24 to wedge the attachment portion 23 against the stop.

[0094] According to other possible embodiments, the locking end may have another shape that can fit a stop that may also have another shape.

[0095] The insert 24 is preferably metallic.

[0096] According to a second embodiment illustrated in figures 7a, 7b and 7c, the sleeve 13 differs from the first embodiment in that it comprises a connecting part 16 which extends the sleeve 13 longitudinally from the annular flange 29. The recess 17 and the internal wall 18 delimiting the recess 17 then extend inside the connecting part 16.

[0097] According to this embodiment, the second opening 33' corresponds to the free end of the connecting part 16.

[0098] The connecting part 16 of the sleeve 13 comprises a first portion 37, connected to the fixing part 14, and a second portion 38 connected to the first portion 37, the first portion 37 having a shape of revolution, a section of which decreases from the fixing part 14 of the sleeve 13 in the direction of the second portion 38, the second portion 38 having a reduced cross-section in a direction of space, in particular along an axis perpendicular to the X axis and to the Y axis.

[0099] In other words, according to a profile view of the blade 7, the connecting part 16 of the sleeve 13 has a cross-section which reduces away from the fixing part 14 and is thus flattened in a direction perpendicular to the axes X and Y. This reduction in the cross-section allows the connecting part 16 to fit into the aerodynamic profile of the fibrous structure 20. The recess 17 thus also has a reduction in section making it possible to form a stop 36.

[0100] When the blade root 22 is positioned inside the sleeve 13, it then extends against at least part of the main portion 19 and inside the connecting part 16 and in particular against the stop 36.

[0101] This stop 36 allows the insert 24 to press the blade root 22 inside the sleeve 13, and in particular against the internal wall 18. For this, the insert 24 has a shape complementary to at least part of the internal wall 18, in particular to the entire internal portion of the fixing part 14 up to the stop 36.

[0102] The connecting part 16 of the sleeve 13, according to a front view of the blade 7, comprises a section which increases with distance from the fixing part 14 and in particular has a dovetail shape.

[0103] This shape is adapted to the complementary shape of the skirt 25 which can thus receive the connecting part 16 of the sleeve 13 so that the connecting part 16 of the sleeve 13 extends between the attachment portion 23 and the skirt 25 of the blade root 22. The skirt 25 thus surrounds the connecting part 16 so as to be in contact with its outer surface and the attachment portion 23 is then pressed against the inner surface of the connecting part 16. In addition, an adhesive joint can be added to the inner surface of the sleeve 13 to improve the mechanical junction with the blade root 22.

[0104] The skirt 25 thus constitutes an additional element for assembling the fibrous structure 20 to the sleeve 13.

[0105] The skirt 25 has a shape complementary to the shape of the connecting part 16 of the sleeve 13. Preferably, the skirt 25 has a dovetail shape, the narrowest part being located at the free end of the skirt 25, which is the end closest to the fixing part 14.

[0106] Thus, the assembly between the fibrous structure 20 and the sleeve 13 can resist the centrifugal force which is exerted on the blade 21 when the vane 7 is rotating.

[0107] Indeed, when the fan is rotating, the blade 7 undergoes centrifugal forces oriented in a radial direction relative to the axis of rotation of the fan, which tend to separate the aerodynamically profiled blade 12 from the sleeve 13. The attachment portion 23 and the skirt 25 make it possible, by their shape and the manner in which they are assembled with the sleeve 13 and the insert 24, to prevent the separation of the blade 12 and the sleeve 13. The sleeve 13 is preferably metallic and monolithic. The attachment portion 14 and the connecting portion 16 are thus inseparable and remain firmly aligned despite the aerodynamic forces exerted on the blade 7.

[0108] According to the second embodiment, the cylindrical body 40 closely matches the main portion 19 and the locking end 42 closely matches the stop 36, which means that when the blade root 22 is positioned in the recess 17 and the insert is also positioned in the recess 17, the blade root 22 is in contact with the main portion 19, the stop 36 and at least a portion of the cylindrical body 40 and the locking end 42.

[0109] According to a preferred variant of this second embodiment, the sleeve 13 also has a hollow portion 18' described for the first embodiment and making it possible to accommodate an excess thickness 23' of the fibrous structure 20.

[0110] According to another variant of the second embodiment, the connecting part may be shorter and for example only comprise the first cylindrical portion 37.

[0111] Blade manufacturing process

[0112] With reference to Figure 8, a manufacturing method 50 of a blade 7 comprises a step 51 consisting of producing the fibrous structure 20 comprising the attachment portion 23 by three-dimensional weaving, the attachment portion 23 being produced by forming gaps in the weaving.

[0113] Preferably, this step also includes the manufacture of the skirt 25 in the fibrous structure 20 by also creating delinks in the weaving.

[0114] Furthermore, the weaving is carried out so as to form the two cavities 26 in which shaping pieces 27 are inserted.

[0115] The method 50 then comprises the step 52 of inserting the attachment portion 23 into the recess 17 of the sleeve 13 and positioning said attachment portion 23 against the internal wall 18.

[0116] In a step 53, the insert 24 is positioned in the recess 17 so as to block the attachment portion 23 against the internal wall 18. Preferably, the cylindrical body 40 blocks a part of the attachment portion 23 against the main portion 19 and the blocking end 42 blocks another part of the attachment portion 23 against the stop 36.

[0117] Preferably, the method 50 further comprises a step 54 consisting of positioning the skirt 25 of the blade root 22 on the connecting part 16 so that the skirt 25 is pressed against the connecting part 16. Once the fibrous structure 20, the sleeve 13 and the insert 24 are assembled, the blade 7 thus formed is inserted into a mold to obtain a preform with an aerodynamic profile. In a step 55, a liquid resin is then injected into the mold according to the RTM process to obtain the single-piece blade 7 shown in FIGS. 9a and 9b. The resin may in particular be an epoxy resin, a thermoplastic resin or a polybismaleimide (BMI) resin.

[0118] When the resin is injected, the latter impregnates the entire fibrous structure 20 and is thus inserted in particular between the insert 24 and the wall 18 and around the connecting part 16. The resin thus makes it possible to maintain the various assembled elements, namely the fibrous structure 20, the sleeve 13 and the insert 24, in a single block.

[0119] Preferably, the embodiment 51 of the fibrous structure 20 comprises the embodiment of a first tab 60 and a second tab 62, the first and second tabs 60 and 62 each comprising two beveled lateral edges 60a, b and 62a, b over at least part of their length. The beveled lateral edges are intended to form together the attachment portion 23. During the insertion 55 of the fibrous structure 20 into the mold, the first and second tabs 60 and 62 are assembled by joining two by two the beveled lateral edges 60a and 60b of the first tab 60 with the beveled lateral edges 62a and 62b of the second tab 62 so as to form a cylindrical attachment portion 23.

Claims

CLAIMS 1. Blade (7) for a turbomachine comprising: - a sleeve (13), comprising a fixing part (14) configured to be connected to a variable timing mechanism of a turbomachine, a through recess (17) being formed in the fixing part (14) of the sleeve (13), the recess (17) being delimited by an internal wall (18) of the sleeve (13) having a length L; - a fibrous structure (20) obtained by three-dimensional weaving of strands, the fibrous structure (20) comprising: - a blade root (22) comprising an attachment portion (23) configured to be inserted into the recess (17) of the fixing part (14) of the sleeve (13), - an aerodynamically profiled blade (12) connected to the blade root (22); - an insert (24), configured to be inserted into the recess (17) of the fixing part (14) of the sleeve (13) and to press the blade root (22) against the internal wall (18) of the sleeve (13), so that the attachment portion (23) is positioned directly in contact with the internal wall of the sleeve (13), and this, over at least 20% of the length L of the internal wall (18) of the sleeve (13).

2. Blade according to claim 1, in which the blade root (22) further comprises a skirt (25) extending around the attachment portion (23) of the sleeve (13) and the fixing portion (14) further comprises an annular flange (29), and in which an end face (25') of the skirt (25) of the blade root (22) is configured to bear against the flange (29).

3. Blade according to claim 1 or 2, in which the internal wall of the sleeve comprises a hollow portion causing a widening of the recess (17) in a radial direction and in which the attachment portion (23) comprises an excess thickness (23”) configured to fit into the hollow portion.

4. Blade according to any one of claims 1 to 3, in which the sleeve (13) further comprises a connecting part (16) in one piece with the fixing part (14) and in which the recess (17) extends, the blade root being configured to be inserted into the connecting part (16).

5. Blade according to claim 4 when it depends on claim 2, in which the connecting part (16) of the sleeve (13) extends between the attachment portion (23) and the skirt (25) of the blade root (22).

6. Blade according to one of claims 1 to 5, in which the sleeve (13) further comprises a stop (36) extending from the internal wall (18), the insert (24) being configured to press the blade root (22) against the stop (36).

7. A blade according to claim 6 when dependent on claims 4 or 5, wherein the stop (36) is formed by a reduction in section of the recess (17) in the connecting portion (16) of the sleeve (13).

8. Blade according to one of claims 4 to 7, wherein a cross section of the connecting part (16) of the sleeve (13) is flattened in one direction.

9. Blade according to one of claims 4 to 8, in which the fixing part (14) of the sleeve (13) has a shape of revolution and the connecting part (16) of the sleeve (13) comprises a first portion (37), connected to the fixing part (14), and a second portion (38) connected to the first portion (37), the first portion (37) having a shape of revolution, a section of which decreases from the fixing part (14) of the sleeve (13) in the direction of the second portion (38), the second portion (38) having a reduced cross-section in a direction of space.

10. Blade according to one of claims 1 to 9, in which the fixing part (14) of the sleeve (13) has an external surface (30) having a shape of revolution in which at least one circular groove (32, 34) is formed, suitable for forming a raceway for at least one bearing.

11. Blade according to one of claims 1 to 10, in which the sleeve (13) is metallic.

12. Method of manufacturing a blade according to one of claims 1 to 11, comprising the following steps: - producing (51) the fibrous structure (20) comprising the attachment portion (23) by three-dimensional weaving, - insert (52) the attachment portion (23) into the recess (17) of the sleeve (13) and against the inner wall (18), - position (53) the insert (24) in the recess (17) so as to block the attachment portion (23) against the internal wall (18), and - inserting (55) the fibrous structure (20), the sleeve (13) and the insert (24) into a mold to obtain a preform with an aerodynamic profile.

13. Method according to claim 12, further comprising a step (55) consisting of injecting a resin into the mold, after insertion of the fibrous structure (20), the sleeve (13) and the insert (24) into said mold, to obtain the blade (7) according to one of claims 1 to 11, said blade being in one piece.

14. Manufacturing method according to claim 12 or 13 when they depend on claim 4, further comprising a step (54) consisting of positioning the skirt (25) of the blade root (22) on the connecting part (16) before inserting the fibrous structure (20), the sleeve (13) and the insert (24).

15. Manufacturing method according to any one of claims 12 to 14, in which the production (51) of the fibrous structure (20) comprises the production of a first tab and a second tab, the first and second tabs each comprising two beveled lateral edges over at least part of their length and being intended to form together the attachment portion (23), and in which, during the insertion (55) of the fibrous structure (20) into the mold, the first and second tabs are assembled by joining two by two the beveled lateral edges of the first tab with the beveled lateral edges of the second tab so as to form a cylindrical attachment portion (23).

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