TOOL FOR MACHINING AN ABRADABLE ANNULAR LAYER OF A FAN CASING OF AN AIRCRAFT TURBOMACHINE AND MACHINING METHOD USING SUCH A TOOL

Abstract

Tool (20) for machining an annular abradable layer (10b) of a fan casing (3) of an aircraft turbomachine, comprising: - a central centering body (30) configured to be fixed to a fan disk (2) of the turbomachine, - a machining tool (50) connected to the central body (30) and comprising at least one machining means (51) configured to come into contact with the abradable layer, and - a first motor (52) for rotating said machining means (51), characterized in that the central body (30) comprises or carries a copy cam (70) which comprises a cam profile (72) which is a function of a desired surface profile for the abradable layer (10b) after machining. Figure for abstract: Fig. 7

Description

Title of the invention: TOOL FOR MACHINING AN ABRADABLE ANNULAR LAYER OF A FAN CASING OF AN AIRCRAFT TURBOMACHINE AND MACHINING METHOD USING SUCH A TOOL Technical field of the invention

[0001] The present invention relates to a tool for machining an abradable annular layer of a fan casing of an aircraft turbomachine as well as a machining method using such a tool. Technical background

[0002] The technical background includes in particular documents WO-A1-2016 / 2023141 and WO-A 1-2023 / 062302.

[0003] A fan casing assembled on an aircraft turbomachine has the main function of ensuring retention in the event of debris ingestion or loss of a fan blade.

[0004] Some of the secondary functions of a fan casing are to ensure mechanical continuity in forces and moments between an air inlet sleeve and an intermediate casing shroud, to allow the fixing of the vein panels, such as the upstream acoustic shroud, the abradable layer support cartridge and the downstream acoustic panel.

[0005] Other functions of the blower housing are to allow attachment of equipment and supports, to meet fire and leak specifications and to allow continuity of electrical current for lightning resistance.

[0006] For example, on a turbomachine, a number of eighteen fan blades can be installed opposite the abradable layer. This abradable layer, frequently made of a solid-colored porous material, crumbles during operation in order to guarantee an optimal aerodynamic flow thanks to the fan blades which come into contact with the layer.

[0007] When not in operation, it is necessary to ensure a certain clearance to ensure the mounting of the fan blades in the fan casing.

[0008] In operation, the inertia of the fan disc, which is composed, among other things, of all the fan blades, causes the disc to move apart in order to fill the mounting clearance but also in order to create an optimal aerodynamic flow.

[0009] To create this aerodynamic vein, the fan blades come into contact with the abradable layer and crumble it as needed.

[0010] In operation, it may happen that, as they crumble, certain detachments of abradable porous material become detached from the rest of the surface.

[0011] This is not the only source of crumbling of the abradable layer because, during operation, the blower may suck in foreign bodies, which can damage the abradable surface.

[0012] These missing surfaces or asperities, of the order of a few micrometers, on one face of the abradable layer sequentially opposite the blades must be reconditioned to avoid in particular losses of performance, cosmetic problems or even risks of additional degradation in the event of non-compliance.

[0013] In order to recondition the abradable annular layer, it is known to dismantle the casing on which the abradable layer is located in its entirety in order to position it in an environment (for example a workshop) allowing the machining and reconditioning of the abradable layer. The dismantling of the casing, its transport to the workshop and then the reverse operations are inefficient, costly and require the presence of a specialized workshop near the casing.

[0014] Therefore, there is a need to improve the efficiency and repeatability of machining an abradable layer of an aircraft turbomachine fan casing.

[0015] The Applicant has already proposed a tool for machining an abradable annular layer of a fan casing in document FR-A1-3 117 390.

[0016] The invention provides an improvement to this type of tooling and in particular improves the machining quality. Summary of the invention

[0017] The invention therefore proposes a tool for machining an abradable annular layer of a fan casing of an aircraft turbomachine, this tool being configured to be at least partly housed in said casing and comprising:

[0018] - a central centering body configured to be attached to a fan disk of the turbomachine, so as to be mobile in rotation around an axis of rotation of the fan disc,

[0019] - a machining tool connected to the central body and comprising at least one means machining configured to come into contact with the abradable layer, and

[0020] - a first motor for driving said machining means in rotation,

[0021] characterized in that the central body comprises or carries a copying cam which comprises a cam profile which is a function of a desired surface profile for the abradable layer after machining, the machining tool being movable relative to the copying cam and being configured to follow the cam profile so that the machining means machines the abradable layer according to the cam profile.

[0022] The tooling, thanks in particular to its central body, can thus be arranged directly inside the fan casing regardless of the positioning of the casing. The tooling according to the invention makes it possible to precisely machine the abradable layer thanks to the copy cam which is selected according to its cam profile. The abradable layer will be machined according to this cam profile which significantly improves the machining quality and in particular the dimensional and geometric conformities of the abradable layer after machining.

[0023] In the present application, the term "surface profile" means the profile (i.e. the general shape) of a surface in cross-section. The surface considered is the internal annular surface of the abradable layer and the profile of this surface is therefore the general shape of this surface when considering a cross-section of this abradable layer.

[0024] The tooling according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: • the machining method is a ball mill; • the tooling comprises a second motor for driving the machining tool in rotation around said axis of rotation; • the or each motor is a brushless type electric motor; • the copy cam is removably and interchangeably mounted on the central body; • the copying cam comprises a flat plate in which an elongated through-hole is formed, this hole comprising a longitudinal edge which defines the desired surface profile, i.e. a shape in axial section of an internal annular surface of the abradable layer; • the plate has a general parallelepiped shape; • the flat plate extends in a plane passing through the axis of rotation; • the machining tool comprises a follower, such as a roller, which cooperates by sliding or rolling with said longitudinal edge; • the copy cam is clamped to the central body by fixing brackets and / or clamping screws; • said machining means is housed in a protective and containment cover for chips and dust, this cover being carried by the tool; • the hood is connected by a pipe to a chip and dust suction pump; • the tooling further comprises a measuring tool connected to the central body and comprising at least one probe configured to bear on said layer, this measuring tool being for example diametrically opposite with respect to the machining tool with respect to said axis of rotation; • the central body is equipped with balancing masses which can be adjusted in position so as to limit the force required to drive the central body in rotation around the axis of rotation; • the tooling also includes formwork extensions intended to be mounted on either side of the abradable layer and to be clamped axially against the abradable layer.

[0025] The invention also relates to a method of machining an abradable annular layer of a fan casing of an aircraft turbomachine, by means of a tool according to one of the preceding claims, comprising the steps consisting of:

[0026] a) determining the desired surface profile for the abradable layer after machining,

[0027] b) selecting a copy cam having a cam profile that matches this surface profile, and removably mounting it on the central body, and

[0028] c) machining the abradable layer according to the cam profile. Brief description of the figures

[0029] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0030] [Fig-1] [Fig.l] is a schematic representation of an axial sectional view of a fan of an aircraft turbomachine,

[0031] [Fig.2] [Fig.2] is a schematic representation of a perspective view of a fan housing,

[0032] [Fig.3] [Fig.3] is a schematic representation of a side view of a crankcase blower and machining tools according to the invention,

[0033] [Fig.4] [Fig.4] is a schematic representation of an axial sectional view of a machining tool according to the invention inserted into a part of a fan disc,

[0034] [Fig.5] [Fig.5] is a schematic representation of a perspective view of a central body of the machining tool according to the invention,

[0035] [Fig.6] [Fig.6] is a schematic representation of an axial sectional view of extensions of the machining tool according to the invention, and

[0036] [Fig.7] [Fig.7] is a schematic representation of a perspective view of a machining tool and a cam for copying the machining tool according to the invention,

[0037] [Fig.8] [Fig.8] is a schematic representation of another perspective view of the machining tool and the copy cam of the machining tool according to the invention,

[0038] [Fig.9] [Fig.9] is a schematic representation of another perspective view of the copy cam of the machining tool according to the invention,

[0039] [Fig. 10] [Fig. 10] is a schematic representation of a perspective and sectional view of the copying cam of the machining tool according to the invention,

[0040] [Fig. 11] [Fig. 11] is a schematic representation of another perspective and sectional view of a part of the machining tooling according to the invention, and

[0041] [Fig. 12] [Fig. 12] is a schematic perspective representation of masses of the machining tool according to the invention of the tool copy cam. Detailed description of the invention

[0042] [Fig.l] partially represents a fan of an aircraft turbomachine.

[0043] Conventionally, a turbomachine comprises from upstream to downstream, that is to say in the direction of flow of the gas flows, a fan, one or more compressors, a combustion chamber, one or more turbines, and a nozzle for ejecting the combustion gases leaving the turbine(s).

[0044] The fan 1 comprises a bladed disc 2 which is surrounded by a fan casing 3, also called a retention casing due to its function of retaining the blades in the event of their breaking, or in the event of debris entering the fan.

[0045] As can be seen in [Fig.2], the fan casing 3 has a generally cylindrical shape with an axis of revolution A.

[0046] It comprises an annular fixing flange 3' at each of its axial ends. These flanges 3' are used to fix the casing 3 to annular walls of the nacelle of the turbomachine or to the shell of a downstream intermediate casing.

[0047] As shown in this [Fig.2], a layer of abradable material 10b is present inside the fan casing 3 while being of revolution in the fan casing 3.

[0048] The fan casing 3 therefore extends around the fan blade disc 2. It therefore comprises an internal cylindrical surface which is provided with an annular layer 10b of abradable material.

[0049] The annular layer 10b of abradable material, hereinafter referred to as the abradable layer 10b, extends around and at a short radial distance from one 2a of the blades, this sequentially during the rotation of the bladed disc 2. The blades 2a can, in operation and successively, rub against the abradable layer 10b and wear it by friction.

[0050] This makes it possible to optimize the radial clearances between the blades 2a and the fan casing 3 which surrounds it and therefore to limit gas leaks at the radially external tips or ends of the blades, and thus to optimize the performance of the turbomachine.

[0051] The abradable layer 10b may be supported by a support cartridge 4 that is solid or has a honeycomb structure. This cartridge 4 is generally riveted or screwed onto the fan casing 3.

[0052] A machining tool 20 according to the invention is shown in [Fig. 3] (outside the casing 3) and in [Fig. 4] (inside the casing 3). Such a tool 20 is configured to machine the abradable layer 10b of the casing 3 of the fan 1 in particular for the purpose of reconditioning this abradable layer 10b.

[0053] The tool 20 comprises for this purpose:

[0054] - a central body 30 for centering, or even for fixing, on the disc 2 of fan of the turbomachine, this central body 30 being intended to be movable in rotation around the axis A of rotation of the fan disk 2,

[0055] - a machining tool 50 connected to the central body 30 and comprising at least one means machining, such as a rotary cutter 51, configured to come into contact with the abradable layer 10b, and

[0056] - a first motor 52 for driving the machining cutter 51 in rotation.

[0057] The tool 20 may further comprise a measuring tool 40 connected to the central body 30 and comprising at least one probe 41 configured to bear on the abradable layer 10b, this measuring tool being movable in rotation around the axis A of the central body 30.

[0058] The tool 20 may further comprise a second motor 32 for driving in rotation at least measuring tools 40 and machining tools 50, around the axis A. Alternatively, this rotation could be carried out manually by an operator around the axis A.

[0059] The machining tools 50 and measuring tools 40 as well as the central body 30 are for example connected to each other by a shaft 90. The shaft extends radially along a dimension substantially smaller than that of an internal diameter of the casing 3 in order to allow the axial insertion of the tooling 20 into the casing 3. The machining tools 50 and measuring tools 40 are in particular substantially diametrically opposed with respect to the axis A.

[0060] The tool 20 can be brought inside the casing 3 by means of a rolling carriage 60, such as that described in document WO-A1-2023 / 062302 for example. The tool 20 can have a mass of between 100 and 150 kg.

[0061] Once the tool 20 is centered relative to the casing 3, it is inserted along the axis A into the casing 3. Once the tool 20 is inserted inside the casing 3, it is fixed to the fan disc 2 by means of a fixing means 31 that the central body 30 comprises.

[0062] The tool 20 further comprises movement means 58 making it possible to move the machining tool 50 in translation relative to the shaft 90, i.e. radially. These movement means 58 thus make it possible to position the milling cutter 51 in contact with the abradable layer in order to be able to adjust the depth of cut and therefore to carry out the machining.

[0063] At least one of the first 52 and second 32 motors is electric and preferably brushless to reduce noise pollution during operation and improve operator comfort during machining.

[0064] Each of the first 52 and second 32 motors can have a separate control. Consequently, they can rotate at two separate rotation speeds. It is then possible to perform a complete rotation of the measuring tool 40 and the machining tool 50 with the probe in contact with the abradable layer to measure its thickness without the milling cutter 51 being rotated.

[0065] The milling cutter 51 can be housed in a cover 53 for protecting and confining chips and dust, this cover 53 being carried by the machining tool 50.

[0066] The cover 53 is here connected by a pipe 54 to a pump (not shown) for suctioning chips and dust. The vacuum cleaner thus makes it possible to prevent any suction of dust by the operators. The cover 53 is for example transparent in order to have a visualization of the cutter 51 and the abradable layer 10b during machining.

[0067] Figures 5 and following show different parts of a more concrete embodiment of the tool 20 according to the invention.

[0068] [Fig. 5] shows the central body 30 of this tool, which has a generally annular shape and which is here carried by the aforementioned carriage 60.

[0069] [Fig.6] shows formwork extensions 62, 64 intended to be mounted on either side of the abradable layer 10b and to be clamped axially against the abradable layer 10b.

[0070] These extensions 62, 64 are used to recondition the abradable layer 10b after its machining. The extensions 62, 64 make it possible to create a formwork for applying the new abradable material.

[0071] A straight spatula 66 is guided in or on the extensions 62, 64 to apply a new abradable in controlled excess thickness.

[0072] Figures 7 to 9 show that the central body 30 comprises or carries a copy cam 70 which comprises a cam profile 72 which is a function of a desired surface profile for the abradable layer 10b after machining.

[0073] The machining tool 50 is movable relative to the copy cam 70 and is configured to follow the cam profile 72 so that the cutter 51 machines the abradable layer 10b according to the cam profile 72.

[0074] The copy cam 70 is preferably removably mounted on the central body 30 in order to be able to choose the copy cam 70 according to its cam profile 72 and thus adapt the cam profile 72 to the fan casing 3 to be machined. The abradable layers 10b of the fan casings of several engines or references of the same engine may have different surface profiles. The number of copy cams 70 available is preferably equal to the number of surface profiles different from these fan casings 3. It is therefore understood that an operator must select the copy cam 70 having the desired surface profile for the abradable layer 10b, and mount this copy cam on the tooling 20.

[0075] The copy cam 70 can be clamped to the central body 30 by fixing brackets 74 and / or clamping screws 76.

[0076] In the example shown, the copying cam 70 comprises a flat plate 80 in which an elongated through-hole 82 is formed. The hole 82 comprises a longitudinal edge 84 which defines the desired surface profile, i.e. a shape in axial section of an internal annular surface of the abradable layer 10b.

[0077] The plate 80 has, for example, a generally parallelepiped shape.

[0078] The plate 80 preferably extends in a plane passing through the axis of rotation A.

[0079] The machining tool 50 may comprise a follower 91, such as a roller, which cooperates by sliding or rolling with the longitudinal edge 84 of the light 82.

[0080] [Fig. 11] shows a micrometric adjustment system 92 for adjusting the depths of machining passes, and a positioning system 93 using conical surfaces and holding screws.

[0081] [Fig. 12] shows that the central body 30 can be equipped with balancing masses 94 adjustable in position so as to limit the force necessary for driving the central body 30 in rotation around the axis of rotation A.

[0082] When not in use, the tool 20 can be stored in a box which can also be used for its transport.

[0083] The present invention also relates to a method for machining an abradable annular layer 10b of a casing 3 of a fan 1 of an aircraft turbomachine, by means of the tooling 20 described above, comprising the steps consisting of:

[0084] a) determining the desired surface profile for the abradable layer 10b after machining,

[0085] b) choosing a copy cam 70 having a cam profile which corresponds to this surface profile, and removably mounting it on the central body, and

[0086] c) machining the abradable layer 10b according to the cam profile.

[0087] During machining, the casing vein may be protected by flanges or the like, such as those described in document WO-A1-2023 / 062302 for example.

[0088] The invention provides several advantages, including:

[0089] - improved ergonomics for operators, particularly in terms of nuisances sound,

[0090] - a dimensional conformity of the abradable layer 41b, which can be detected live during machining by the probe 4701,

[0091] - a faster reconditioning time in order to reduce as much as possible the engine downtime,

[0092] - increased repeatability of reconditioning,

[0093] - a high level of security for operators,

[0094] - adaptability of the tooling to different surface profile configurations, thanks to the interchangeability of the copy cam, etc.

Claims

Claims

1. Tool (20) for machining an abradable annular layer (10b) of a fan casing (3) of an aircraft turbomachine, this tool (20) being configured to be at least partly housed in said casing (3) and comprising: - a central centering body (30) configured to be fixed to a fan disc (2) of the turbomachine, so as to be movable in rotation about an axis of rotation (A) of the fan disc (2), - a machining tool (50) connected to the central body (30) and comprising at least one machining means (51) configured to come into contact with the abradable layer, and - a first motor (52) for driving in rotation said machining means (51), characterized in that the central body (30) comprises or carries a copy cam (70) which comprises a cam profile (72) which is a function of a desired surface profile for the abradable layer (10b) after machining,the machining tool (50) being movable relative to the copy cam (70) and being configured to follow the cam profile (72) so that the machining means (51) machines the abradable layer (10b) according to the cam profile (72), and in that the copy cam (70) comprises a flat plate (80) in which a through-hole (82) of elongated shape is formed, this hole (82) having a longitudinal edge (84) which defines the desired surface profile, the machining tool (51) comprising a follower (91) which is engaged in the hole (82) and which cooperates by sliding or rolling with said longitudinal edge (84).,

2. Tooling (20) according to claim 1, wherein the machining means is a ball end mill (51).

3. Tooling (20) according to claim 1 or 2, in which it comprises a second motor (32) for driving the machining tool (50) in rotation around said axis of rotation (A).

4. Tooling (20) according to one of the preceding claims, in which the or each motor (32, 52) is an electric motor of the brushless type.

5. Tooling (20) according to one of the preceding claims, in which the copying cam (70) is removably and interchangeably mounted on the central body (30).

6. Tooling (20) according to one of the preceding claims, in which the plate (80) has a generally parallelepiped shape.

7. Tooling (20) according to one of the preceding claims, in which the flat plate (80) extends in a plane passing through the axis of rotation.

8. Tooling (20) according to one of the preceding claims, in which the follower (91) is a roller.

9. Tool (20) according to one of claims 5 to 8, in which the copy cam (70) is clamped on the central body (30) by fixing brackets (74) and / or clamping screws (76).

10. Tool (20) according to one of the preceding claims, in which said machining means (51) is housed in a cover (53) for protecting and confining chips and dust, this cover (53) being carried by the machining tool (50).

11. Tool (20) according to claim 10, in which the cover (53) is connected by a pipe (54) to a chip and dust suction pump.

12. Tooling (20) according to one of the preceding claims, in which it further comprises a measuring tool (40) connected to the central body (30) and comprising at least one probe (41) configured to bear on said layer (10b), this measuring tool (40) being for example diametrically opposite relative to the machining tool with respect to said axis of rotation (A).

13. Tool (20) according to one of the preceding claims, in which the central body (30) is equipped with balancing masses (94) adjustable in position so as to limit the force necessary for driving the central body in rotation around the axis of rotation (A).

14. Tooling (20) according to one of the preceding claims, in which it further comprises formwork extensions (62, 64) intended to be mounted on either side of the abradable layer (10b) and to be clamped axially against the abradable layer (10b).

15. Method of machining an abradable annular layer (10b) of a casing (3) of a fan (1) of an aircraft turbomachine, by means of a tool (20) according to one of the preceding claims, comprising the steps consisting of: a) determining the desired surface profile for the abradable layer (10b) after machining, b) selecting a copy cam (70) having a cam profile (72) which corresponds to this surface profile, and removably mounting it on the central body (30), and c) machining the abradable layer (10b) according to the cam profile (72).

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