one-piece turbomachine blade

Abstract

The invention relates to a blade (7) for a turbomachine comprising: - a sleeve (13), including a fastening part (14) configured to be connected to a variable pitch mechanism of a turbomachine, a through recess (17) being formed in the fastening part (14) of the sleeve (13), the recess (17) being delimited by an internal wall of the sleeve (13); - a fibrous structure (20) obtained by three-dimensional weaving of strands, the fibrous structure (20) comprising: - a blade root (22) including an attachment portion (23) configured to be inserted into the recess (17) of the fastening 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 fastening part (14) of the sleeve (13) and to press the blade root (22) against the inner wall (18) of the sleeve (13). Figure for the abbreviation: Fig. 4c

Description

Title of the invention: single-block turbomachine blade Field of invention

[0001] The invention relates generally to the field of turbomachines, and in particular to turbomachine blades.

[0002] The invention relates more particularly, but not exclusively, to a blade intended to be used in an unducted fan rotor of an aircraft engine. Technological background

[0003] The advantage of unducted fan engines is that the diameter of the fan is not limited by the presence of a shroud, so that it is possible to design an engine with a high dilution ratio (known as "By Pass Ratio" or BPR), and consequently reduced fuel consumption. Thus, in this type of engine, the fan blades can have a large span.

[0004] 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.

[0005] However, the design of such blades requires taking into account opposing constraints.

[0006] On the one hand, the dimensioning of these blades must allow 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.

[0007] On the other hand, it is also necessary to guarantee resistance to the mechanical stresses that can be exerted on these blades while limiting their acoustic signature.

[0008] Furthermore, on architectures with unducted fans, the engine is generally started with a very open timing. Indeed, a very open timing allows the power to be consumed by the torque, which ensures machine safety by guaranteeing low fan speeds.

[0009] However, with a very open pitch, the blades undergo a turbulent aerodynamic flow, completely detached, which generates a broadband vibratory excitation. In particular, on blades with a wide chord and large span, the bending force is intense, although the engine speed is not maximum.

[0010] In normal operation, namely during the ground and flight phases, the pitch is modified so that the pitch angle is narrower. 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 not ducted, 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 IP 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.

[0011] These blades can be made of metallic material. Although blades made of metallic material have good mechanical strength, they nevertheless have the disadvantage of having a relatively large mass.

[0012] The manufacture of blades from composite material is an interesting solution for reducing the weight of the blades. However, blades made from composite material can be fragile in view of 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 hub of the fan rotor, at the level of the blade root.

[0013] In order 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 allow, 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.

[0014] These solutions, however, have the disadvantage of having to manufacture several elements in materials that may be different and of having to assemble them using fixing means. Such blades can therefore take a relatively long time to manufacture. BRIEF DESCRIPTION OF THE INVENTION

[0015] 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 resisting 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.

[0016] Another object of the invention is to propose a blade comprising a composite material and adapted to be used 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.

[0017] For this purpose, according to a first aspect of the invention, there is proposed a blade for a turbomachine comprising: - 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; - a fibrous structure obtained by three-dimensional weaving of strands, the fibrous structure comprising: - a blade root comprising an attachment portion configured to be inserted into the recess of the attachment part, - an aerodynamically profiled blade connected to the blade root; - an insert, configured to be inserted into the recess of the fixing part of the sleeve and to press the blade root against the internal wall of the sleeve.

[0018] The blade is thus formed from 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 fibrous 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 fibrous structure is thus firmly assembled with the blade root.

[0019] The blade 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 are limited in number, the blade is quick to manufacture. 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 portion further comprises an annular flange, and an end face of the skirt of the blade root is configured to bear against the flange; - the inner 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 fit into the hollow portion; - the sleeve further comprises a one-piece connecting part with the fixing part and in which the recess extends, the blade root being configured to be inserted into the connecting part; - the connecting part 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 part sleeve connection; - a cross-section of the connecting part of the sleeve is flattened in one direction; - the fixing part 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.

[0020] According to a second aspect, the invention proposes a method of manufacturing a blade according to the first aspect, said method comprising the following steps: - produce the fibrous structure comprising the attachment portion by three-dimensional weaving, - insert the attachment portion into the recess of the sleeve and against the internal wall, - position the insert in the recess so as to block the attachment portion against the internal wall, and - insert the fiber structure, the sleeve and the insert into a mold to obtain an aerodynamically profiled preform.

[0021] The method may further comprise a step of injecting a resin into the mold, after insertion of 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.

[0022] The method may also comprise a step of positioning the skirt of the blade root on the connecting part before inserting the fibrous structure, the sleeve and the insert.

[0023] 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 lateral edges beveled over at least part of their length and being intended to form together the attachment portion, and, during the insertion of 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.

[0024] 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.

[0025] According to a fourth aspect, the invention proposes a turbomachine comprising a fan according to the third aspect.

[0026] 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. Brief description of the Figures

[0027] Other characteristics and advantages of the invention will appear on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which:

[0028] [Fig-1] [Fig.l] schematically represents an example of an engine including an unducted blower;

[0029] [Fig.2] [Fig.2] schematically represents a fan blade according to an embodiment of the invention assembled to a timing mechanism;

[0030] [Fig.3] [Fig.3] schematically represents a fan blade according to a first embodiment of the invention;

[0031] [Fig.4a] [Fig.4a] schematically represents a sleeve according to a first embodiment of the invention in a perspective view;

[0032] [Fig.4b] [Fig.4b] schematically represents the sleeve of [Fig.4a] in a profile view;

[0033] [Fig.4c] [Fig.4c] schematically represents the sleeve of figures 4a and 4b in which the attachment portion and the insert are inserted;

[0034] [Fig.4d] [Fig.4d] schematically represents the sleeve / attachment portion / insert assembly of [Fig.4c] inserted into the wedging mechanism;

[0035] [Fig.5a] [Fig.5a] schematically represents a fibrous structure according to an embodiment in partial and front view;

[0036] [Fig.5b] [Fig.5b] schematically represents the fibrous structure of [Fig.5a] in a cross-sectional view;

[0037] [Fig.5c] [Fig.5c] schematically represents the attachment portion of the fibrous structure of Figures 5a and 5b in a cross-sectional view;

[0038] [Fig.6] [Fig.6] schematically represents an insert according to one embodiment of the invention;

[0039] [Fig.7a] [Fig.7a] schematically represents a sleeve according to a second embodiment of the invention in a perspective view;

[0040] [Fig.7b] [Fig.7b] schematically represents the sleeve of [Fig.7a] in a profile view;

[0041] [Fig.7c] [Fig.7c] schematically represents a fan blade according to a second embodiment of the invention;

[0042] [Fig.8] [Fig.8] schematically represents a method of manufacturing a blade according to an embodiment of the invention;

[0043] [Fig.9a] [Fig.9a] represents the blade obtained according to the method of [Fig.8] in front view; and

[0044] [Fig.9b] [Fig.9b] represents the blade obtained according to the method of [Fig.8] in profile view. Detailed description of an example of implementation

[0045] In [Fig.l], 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 [Fig.l]).

[0046] 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.

[0047] In the example illustrated in [Fig.l], 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).

[0048] 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.

[0049] The invention is applicable to turboprop type architectures (comprising a single fan rotor).

[0050] In [Fig.l], 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.

[0051] As illustrated in [Fig.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 engine performance 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 around a pitch axis Y. More precisely, the blade root 9 is rotatably mounted inside a attachment device 10 arranged in the hub 6, by means of balls 11 or other rolling elements.

[0052] 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 operating, in order to generate lift. On the other hand, the blade root 9 is intended to extend outside the air stream.

[0053] 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.

[0054] 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.

[0055] The fibrous structure 20 also comprises a blade 21 with an aerodynamic profile connected to the blade root 22.

[0056] 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.

[0057] 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.

[0058] The blade 7 can thus withstand significant aerodynamic forces while having a limited mass and can thus be used with a variable timing 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.

[0059] With reference to [Fig.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.

[0060] 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.

[0061] As illustrated in [Fig.5b], the fibrous 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 an 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.

[0062] 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.

[0063] The matrix typically comprises an organic material (thermosetting, thermoplastic or elastomer) 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.

[0064] 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.

[0065] 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.

[0066] Concerning the formation of the attachment portion 23 and as illustrated in [Fig.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 the loads me- channels between blade 21 and blade root 22.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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 lighten the mass of the blade 12 while allowing it to retain its aerodynamic shape.

[0071] The rigid material forming the shaping part(s) is preferably honeycombed, for example a foam, and formed for example from previously machined polymethacrylimide (PMI). Alternatively, the rigid honeycombed material may be a previously sealed aluminum honeycomb material.

[0072] 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.

[0073] However, according to a possible embodiment, the cavities can remain empty and not be filled with filling pieces.

[0074] According to this first embodiment and with reference to figures 3, 4a to 4d, the fixing part 14 has a symmetry of revolution around the Y axis. Furthermore, the fixing part 14 comprises an external surface 30 having different reliefs.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] The sleeve 13 is preferably metallic and monolithic.

[0079] 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”.

[0080] According to a possible alternative embodiment, the hollow portion may have another shape and may be placed in another position along the wall 18.

[0081] 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.

[0082] [Fig.4d] represents 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.

[0083] With reference to [Fig. 6], the insert 24 comprises a cylindrical body 40 comprising a free end 41 and a locking end 42 opposite the free end 4L. The locking end 42 is, in this embodiment, a rounded end. According to the variant 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.

[0084] According to other possible embodiments, the locking end may have a another shape that can fit a stop that can also have another shape.

[0085] The insert 24 is preferably metallic.

[0086] 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.

[0087] 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 whose section 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.

[0088] 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.

[0089] 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.

[0090] 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 a part of the internal wall 18, in particular to the entire internal portion of the fixing part 14 up to the stop 36.

[0091] 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.

[0092] 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.

[0093] The skirt 25 thus constitutes an additional element for assembling the fibrous structure 20 to the sleeve 13.

[0094] 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.

[0095] 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.

[0096] 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 virtue of 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.

[0097] The sleeve 13 is preferably metallic and monolithic. The fixing part 14 and the connecting part 16 are thus inseparable and remain firmly aligned despite the aerodynamic forces exerted on the blade 7.

[0098] 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.

[0099] 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.

[0100] According to another variant of the second embodiment, the connecting part may be shorter and for example only comprise the first cylindrical portion 37. Method of manufacturing the blade

[0101] With reference to [Fig.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.

[0102] Preferably, this step also includes the manufacture of the skirt 25 in the fibrous structure 20 by also creating delinks in the weaving.

[0103] Furthermore, the weaving is carried out so as to form the two cavities 26 in which shaping pieces 27 are inserted.

[0104] The method 50 then comprises the step 52 consisting 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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 portion (14) configured to be connected to a variable pitch mechanism of a turbomachine, a through recess (17) being formed in the fixing portion (14) of the sleeve (13), the recess (17) being delimited by an internal wall of the sleeve (13); - 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 portion (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).

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

3. A blade according to claim 1 or 2, wherein the inner wall of the sleeve comprises a hollow portion causing the recess (17) to widen in a radial direction and wherein 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) integral 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. A blade according to claim 4 when dependent on claim 2, wherein the connecting portion (16) of the sleeve (13) extends between the attachment portion (23) and the skirt (25) of the blade root (22).

6. A blade according to one of claims 1 to 5, wherein the sleeve (13) further comprises a stop (36) extending from the inner 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 part (16) of the sleeve (13).

8. A blade according to one of claims 4 to 7, wherein a cross-section of the connecting portion (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 of which a section 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. A 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, - inserting (52) the attachment portion (23) into the recess (17) of the sleeve (13) and against the internal wall (18), - positioning (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) 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 monobloc.

14. Manufacturing method according to claim 12 or 13 when dependent on claim 4, further comprising a step (54) 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 lateral edges beveled 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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