Blower hub assembled by friction welding

Abstract

This fan hub (8) comprises an annular central body (10) comprising radial vents (12) each configured to hold a fan blade in position, the fan hub (8) further comprising an upstream shroud (14) and a downstream shroud (16), the upstream shroud (14) and the downstream shroud (16) each being annular and fixed to the central body (10) by inertial friction welding. Figure for the abstract: Fig. 3

Description

Title of the invention: Fan hub assembled by friction welding Technical field

[0001] The present invention relates to methods of manufacturing fan “hub” type parts, this type of part being the equivalent of fan discs on turbojets.

[0002] In particular, the present invention relates to the manufacture of fan hubs by friction welding. Previous techniques

[0003] A fan hub of an aircraft engine, a type of part equivalent to the fan disc, makes it possible to support the fan blades as well as certain bearings, the blades extending radially beyond the fan hub so as to form said fan.

[0004] The fan hub allows the transmission of engine torque to the blades, the fan hub being further connected to the engine shaft of the aircraft engine. It thus provides propulsion in conjunction with the blades and the blade setting system located at the heart of the fan hub, the blade setting system being directly connected to the root of each blade and orienting them according to an input instruction.

[0005] The fan hub is subject to major manufacturing constraints in order to guarantee the safety of the aircraft and its passengers. In particular, the mechanical properties of the fan hub must prevent any breakage of its material and / or any other hazardous effect. The criterion of resistance to damage tolerance being one of the major criteria to be satisfied.

[0006] There are currently two different manufacturing methods for making a fan hub.

[0007] A first manufacturing method comprises implementation by foundry as well as shaping by conventional machining.

[0008] The second manufacturing method includes implementation by forging as well as shaping by conventional machining.

[0009] For these two methods, the fan hub produced is in one piece and the machining is carried out in the mass after obtaining by casting or forging.

[0010] The first method of implementation by casting allows the production of more complex shapes and closer to the needs for a fan hub. This also allows an optimization of the quantity of material required, and thus the reduction of costs linked to the quantity of material. This method requires little machining, these final operations being necessary only to redraw precise surfaces and interfaces, and is easily industrialized. However, the material's performance in terms of mechanical strength is not sufficient.

[0011] The second method of implementation by forging requires starting from a block of material whose volume is larger than the final requirement, which represents a high material cost. In addition, forging does not allow for the removal of as much material or the production of complex optimized shapes such as by casting, the hub obtained then being more massive. Nevertheless, forging makes it possible to obtain superior mechanical properties of the material which are necessary for the production of the fan hub: this method is necessary because it guarantees the manufacture of a fan hub satisfying the safety criteria required in the aeronautical environment.

[0012] [Fig.l] schematically shows a block of material 2 from which a fan hub 4 can be forged. [Fig.l] more precisely shows a radial section of the block of material revealing a radial mouth 6 configured to hold a fan blade in position.

[0013] The second method has other disadvantages, such as the need to find a capable blacksmith as well as the degradation of the properties of the material at the heart of the block of material. Indeed, this second method involves a step of quenching the block of material, which modifies the properties of the material located on the outside of the block of material differently from the properties of the material located inside, for example at point P, due to its excessive massiveness. The properties of the material are thereby reduced, harming the safety of the aircraft's flights. Statement of the invention

[0014] The present invention therefore aims to overcome the aforementioned drawbacks and to provide a fan hub which perfectly meets the needs relating to flight safety with sufficient material characteristics, and which allows large-scale industrial production with production costs deemed acceptable.

[0015] The present invention relates to a fan hub comprising an annular central body comprising radial vents each configured to hold a fan blade in position, the fan hub further comprising an upstream shroud and a downstream shroud, the upstream shroud and the downstream shroud each being annular and fixed to the central body by inertial friction welding.

[0016] Thus, the proposed solution makes it possible to assemble a fan hub with several parts, making it possible to obtain the best mechanical properties of the material without reduction linked to the massiveness, a gain in mass, and possible industrialization at low cost. The separation into three parts also makes it possible to obtain easier accessibility for machining operations before assembly.

[0017] Advantageously, the central body, the upstream ferrule and the downstream ferrule are each produced independently by forging.

[0018] Advantageously, each radial mouth comprises a set of shims configured to position and maintain a fan blade in a fixed position radially relative to the axis of rotation of said fan, so that said fan blade does not escape when subjected to a centrifugal force due to the rotation of said fan.

[0019] Advantageously, the fan hub comprises at least two tangential force absorption yokes fixed to the upstream shroud, at least one tangential force absorption yoke being an emergency yoke.

[0020] Advantageously, the tangential force absorption yokes are fixed to the upstream shell by linear friction welding.

[0021] Advantageously, the downstream ferrule is mechanically connected to a part transmitting the engine torque.

[0022] Advantageously, the central body comprises titanium and / or an aluminum alloy.

[0023] The present invention also relates to an aircraft engine comprising a fan hub as defined above.

[0024] The present invention also relates to a method of manufacturing a fan hub as defined above, the method comprising the following steps:

[0025] - Production of the central body, the upstream shell and the downstream shell from three blocks of matter; and

[0026] - Fixing the downstream ferrule and the upstream ferrule to the central body by welding by inertial fiction.

[0027] Advantageously, the step of producing the central body, the upstream ferrule and the downstream ferrule is carried out by forging and includes a heat treatment step.

[0028] Advantageously, the method further comprises a step of fixing the tangential force absorption yokes to the upstream shell by linear friction welding.

[0029] The present invention therefore relates to a fan hub obtained directly by the method defined above. Brief description of the drawings

[0030] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0031] [Fig.l] which has already been mentioned is a schematic sectional view of a block of material from which a fan hub according to the state of the art can be forged;

[0032] [Fig.2] is a schematic view of a fan hub according to the invention;

[0033] [Fig.3] is a detail of [Fig.2];

[0034] [Fig.4] is a schematic sectional view of a block of material from which a central body of a fan hub according to the invention can be forged; and

[0035] [Fig.5] is a schematic representation of the steps of the method of manufacturing a fan hub according to the invention.

[0036] Detailed description of at least one embodiment

[0037] [Fig.2] schematically shows a fan hub 8, a type of part equivalent to the fan disc, according to the invention.

[0038] [Fig.3] also shows schematically a detail of [Fig.2] cut radially.

[0039] The fan hub 8 is intended to be installed in a fan of an aircraft engine, the fan comprising a blade timing system positioned in the center of the fan hub 8. The fan hub 8 notably allows the transmission of the engine torque by connecting a part transmitting the engine torque to the fan blades. The fan hub 8 has as its central axis the axis of rotation of the fan.

[0040] The fan hub 8 comprises an annular central body 10 comprising a plurality of radial mouths 12 each configured to hold a fan blade in position and associated bearings allowing rotation of the fan blade (not shown).

[0041] Each radial mouth 12 is configured to hold a fan blade in position, in other words comprises a set of shims positioning and holding said fan blade in a radial position relative to the axis of rotation of said fan. Each fan blade is also held fixed radially by the set of shims, so that it does not escape when it is subjected to a centrifugal force due to the rotation of the fan.

[0042] The fan hub 8 further comprises an upstream shroud 14 and a downstream shroud 16.

[0043] The upstream 14 and downstream 16 ferrules are annular and have a diameter substantially equal to the diameter of the central body 10.

[0044] The central body 10 comprises an upstream end 18 intended to be positioned towards the front of the aircraft engine when the fan hub 8 is installed in the aircraft engine.

[0045] Similarly, the central body 10 also comprises a downstream end 20 intended to be positioned towards the rear of the aircraft engine.

[0046] The upstream ferrule 14 is fixed to the upstream end 18 of the central body 10 by inertial friction welding.

[0047] Similarly, the downstream ferrule 16 is fixed to the downstream end 20 of the central body 10 by inertial friction welding.

[0048] The downstream shroud 16 is for example mechanically connected to a part transmitting the engine torque of the aircraft engine, so as to transmit the engine torque to the central body 10 and to the fan blades.

[0049] Inertial friction welding is carried out by bringing an annular surface of the upstream ferrule 14 and an annular surface of the downstream ferrule 16 into contact with the central body 10, as well as by rotating the upstream ferrules 14 and downstream ferrules 16 relative to the central body 10, so that the heat released by the friction of the surfaces against the central body 10 allows the formation of welds 22.

[0050] Before inertial friction welding, the central body 10, the upstream shell 14 and the downstream shell 16 are each produced by forging. Forging makes it possible to obtain superior mechanical properties of the material which are necessary to meet the safety criteria required in the aeronautical environment. Variants to forging can also be used if the properties of the final material meet the safety criteria required by aeronautical standards.

[0051] In particular embodiments, the central body 10, the upstream ferrule 14 and the downstream ferrule 16 comprise the same materials, or different materials depending on the needs. In a particular embodiment, the central body 10 and / or the upstream ferrule 14 and / or the downstream ferrule 16 comprises titanium and / or an aluminum alloy. Titanium and / or an aluminum alloy in particular make it easier to recycle unused material scraps during forging.

[0052] Optionally, the fan hub 8 comprises one or more yokes 24 for absorbing tangential forces, the yokes 24 being, for example, fixed to the upstream shroud 14.

[0053] In a particular embodiment, the yokes 24 are fixed to the upstream shell 14 by linear friction welding.

[0054] Linear friction welding is carried out by bringing into contact a surface of the upstream ferrule 14 facing the center of the ring formed by said upstream ferrule 14 and a surface of each yoke 24, then by linear friction of the yokes 24 against the upstream ferrule 14, so that the heat released by the friction of the surfaces allows the formation of a weld 26.

[0055] Linear friction welding is advantageous, especially compared to a simple bolted connection, the weld 26 being more resistant and making it possible to reduce the mass of the fan hub 8 while stiffening and making the interface between the upstream shell 14 and the tangential force absorption yokes 24 more robust.

[0056] A yoke 24 for absorbing tangential forces more precisely comprises a body 28 at the end of which a connecting means 30 is fixed.

[0057] The connecting means 30 makes it possible to mechanically connect a blade setting system (not shown) located in the center of the fan hub 8 to the upstream shroud 14, so as to prevent twisting of the blades or the fan. The tangential forces have concentric circles as their direction around the central axis of the fan hub 8.

[0058] The fan hub 8 comprises a yoke 24 for absorbing tangential forces, and a second emergency yoke 24B for absorbing tangential forces, this emergency yoke 24B being used only when the yoke 24 for absorbing tangential forces is faulty.

[0059] [Fig. 4] schematically shows a block of material 32 from which the central body 10 of the fan hub 8 can be forged. [Fig. 4] more precisely shows a radial section of the block of material 32 revealing a radial mouth 12 configured to hold a fan blade in position.

[0060] The upstream 14 and downstream 16 ferrules being fixed subsequently, the block of material 32 is less massive than the block of material 2 illustrated in [Fig.l]. Less material is therefore used and the forging and then machining time is reduced.

[0061] Furthermore, in the case where the forging of the block of material 32 comprises a step of quenching said block of material, the point P will be closer to the outside of the block of material 32 than in the block of material 2 illustrated in [Fig.l]. The invention therefore makes it possible to achieve the material properties necessary for the safety of aircraft flights, unlike the material characteristics obtained from the part corresponding to the example in [Fig.l].

[0062] The fan hub 8 is in particular produced by the manufacturing method 34, the steps of which are illustrated in [Fig.5].

[0063] In a first step 36, the central body 10, the upstream ferrule 14 and the downstream ferrule 16 are produced from three blocks of material, including the block of material 32.

[0064] This step 36 is carried out by forging and includes a step 38 of heat treatment of the quenching type in order to improve the material characteristics, in particular the elastic resistance. More precise machining of the central body 10, the upstream ferrule 14 as well as the downstream ferrule 16 can also be carried out in order to produce certain details on these parts.

[0065] Then a step 40 is carried out of fixing the downstream ferrule 16 as well as the upstream ferrule 14 to the central body 10 by inertial friction welding.

[0066] Finally, a step 42 of fixing a yoke 24 for absorbing tangential forces to the upstream shell 14 can be carried out. This fixing step 42 is for example carried out by linear friction welding.

Claims

Claims

1. Fan hub (8), characterized in that it comprises an annular central body (10) comprising radial mouths (12) each configured to hold a fan blade in position, the fan hub (8) further comprising an upstream shroud (14) and a downstream shroud (16), the upstream shroud (14) and the downstream shroud (16) each being annular and fixed to the central body (10) by inertial friction welding.

2. The fan hub (8) of claim 1, wherein the central body (10), the upstream ferrule (14) and the downstream ferrule (16) are each made independently by forging.

3. A fan hub (8) according to one of claims 1 and 2, wherein each radial mouth (12) comprises a set of shims configured to position and maintain a fan blade in a fixed position radially relative to the axis of rotation of said fan, such that said fan blade does not escape when subjected to a centrifugal force due to the rotation of said fan.

4. Fan hub (8) according to any one of claims 1 to 3, comprising at least two tangential force absorption yokes (24; 24B) fixed to the upstream shell, at least one tangential force absorption yoke being an emergency yoke (24B).

5. Fan hub (8) according to claim 4, in which the tangential force absorption yokes (24; 24B) are fixed to the upstream shell (14) by linear friction welding.

6. Fan hub (8) according to any one of claims 1 to 5, in which the downstream ferrule (16) is mechanically connected to a part transmitting the engine torque.

7. A fan hub (8) according to any one of claims 1 to 6, wherein the central body (10) comprises titanium and / or an aluminum alloy.

8. Aircraft engine characterized in that it comprises a fan hub (8) according to any one of claims 1 to 7.

9. Method (34) for manufacturing a fan hub (8) according to any one of claims 1 to 8, characterized in that it comprises the following steps: - Production of the central body (10), of the upstream shroud (14) and of the downstream ferrule (16) from three blocks of material (step 36); and - Fixing of the downstream ferrule (16) and the upstream ferrule (14) to the central body (10) by inertial fiction welding.

10. Method (34) according to claim 9, in which the step (36) of producing the central body (10), the upstream ferrule (14) and the downstream ferrule (16) is carried out by forging and comprises a step (38) of heat treatment, the method further comprising a step (42) of fixing a yoke (24; 24B) for taking up tangential forces to the upstream ferrule (14) by linear friction welding.

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