METHOD FOR ATTACHING AT LEAST TWO DISCS TO A TURBOMACHINE ROTOR

Abstract

The invention relates to a method (400) for fixing at least two rotor discs of an aircraft turbomachine, the discs being stacked one on top of the other along a vertical axis of revolution passing through the center of said discs, the discs having annular flanges that are applied axially to one another and that include screw receiving holes, the screws each having a head and a threaded shank passing through the holes in the flanges and receiving a nut, the method comprising the following steps: installing the screws on a mounting member, the member and the screws forming a fastening assembly; positioning the fastening assembly on the disc flanges; installing and tightening the nuts onto the free ends of said shanks until they are secure; removing the mounting member. Figure for the abstract: Figure 5

Description

Title of the invention: METHOD FOR ATTACHING AT LEAST TWO DISCS TO A TURBOMACHINE ROTOR Technical field of the invention

[0001] The present invention relates to a method for fixing at least two rotor discs of an aircraft turbomachine. Technological background

[0002] An aircraft turbomachine comprises at least one rotor, for example a turbine rotor, having bladed wheels connected to each other. A wheel comprises a disc 200 carrying blades on its periphery.

[0003] Figure 1 shows an example of a rotor disc 200 of an aircraft turbomachine. The disc 200 comprises an annular body 206 extending about an axis of revolution A and including at least one annular flange 202 radially internal to the axis of revolution A (i.e., the annular flange extends in a direction perpendicular to the axis of revolution A, while approaching this axis of revolution A), this flange 202 having screw holes 204 parallel to the axis of revolution A. The rotor comprises a stack of discs such as that illustrated in Figure 1. The discs are stacked one on top of the other and then fastened together to form the rotor.

[0004] With reference to [Fig.2], an example of two disks stacked one 200a on top of the other 200b along the axis of revolution A is illustrated.

[0005] In operation, the axis of revolution A is generally horizontal. However, for assembly, the disks are positioned so that the axis A is vertical, as illustrated in [Fig.2] for example.

[0006] The discs 200a, 200b are fixed to each other by means of screws. The screws are evenly distributed around the axis of revolution A. [Fig. 2] shows only one of these screws 300. The following description concerns only one screw but applies to all the fixing screws.

[0007] Each screw 300 is parallel to the axis of revolution A and has a head 300a located above the respective flanges 202a, 202b of the discs 200a and 200b. Each screw 300 also has a threaded rod 300b which passes through the holes 204a, 204b of the flanges 202a, 202b and which receives a nut 300c located below the flanges 202a, 202b.

[0008] The nuts are often tightened using two tightening tools as illustrated in [Fig. 3]. The tightening tools are, for example, a torque wrench 500 and a tightening wrench 502. The tightening wrench 502 is used to hold the head 300a of the screws 300 in place, and the torque wrench is used to tighten the nuts 300c.

[0009] However, this fastening method is not ergonomic. Indeed, an operator is forced to use both hands to tighten each nut 300c, which can be complex when the number of screws to be tightened is high (for example 49).

[0010] In addition, there may be a risk of damaging the discs when removing the screwing tools 500, 502 at the end of the disc fixing operation (risk of impacts between the tools and the discs).

[0011] It may therefore be desirable to provide a method of fixing the discs which makes it possible to overcome at least some of the aforementioned problems and constraints and which is as simple and efficient as possible. Summary of the invention

[0012] A method for fixing at least two discs of a rotor of an aircraft turbomachine is therefore proposed, the discs being stacked one on top of the other along a vertical axis of revolution passing through the center of said discs, the discs having internal radial annular flanges that are applied axially to one another, the flanges having screw reception holes, these screws being inserted into the holes of the flanges so as to be parallel to said axis of revolution, each screw having a head and a threaded shank that passes through the holes of the flanges and receives a nut, the fixing method being characterized in that it comprises the following steps: a. setting up the screws on a mounting member in the shape of an angular sector, the mounting member comprising a first face having holes of complementary shapes to the screw heads, the screw heads being engaged in these holes so that the threaded rods protrude from said face of the mounting member and extend parallel to each other, the mounting member and the screws set up forming a fixing assembly; b. positioning of the fastening assembly on the disc flanges, the screw flanges being previously applied axially to one another and their screw receiving holes being aligned axially with each other, the fastening assembly being mounted on one side of the flanges so that the threaded rods of the screws pass through the holes in the flanges until their free ends protrude from the opposite side of the flanges; c. Installation and tightening of the nuts onto the free ends of the threaded rods until they are secured on the opposite side of the flanges; and d. removal of the mounting element from the screw heads.

[0013] Thus, thanks to the invention, it is possible to improve ergonomics during the disc mounting operation while reducing the risk of damage to the discs and surrounding parts. Disc mounting is therefore facilitated.

[0014] Indeed, it is easier to mount the screws on the mounting member than directly on the flanges. Several screws can be mounted simultaneously on the member, which is not the case when mounting directly on the flanges, where the screws are inserted one by one. The invention therefore saves time.

[0015] Furthermore, the screws are already perfectly positioned relative to each other when the mounting device is used. Thus, the mounting device can be manipulated without interfering with the screws during their positioning and insertion into the holes in the disc flanges.

[0016] Furthermore, it is no longer necessary to use two screw-driving tools simultaneously, one to hold the screw heads in place and the other to tighten the nuts. Indeed, the mounting device holds the screw heads securely, and only one screw-driving tool is needed to attach the discs. Thus, the discs can be easily attached by a single operator.

[0017] The invention can also enable savings in energy and material resources, as the discs are fixed without damaging surrounding parts, for example, but not limited to, the discs or moving rings. Indeed, damage to one of the rotor parts may necessitate the manufacture of a new part to replace the damaged one. This can involve an expenditure of energy (electrical, thermal, etc.) and the use of materials for manufacturing the new part.

[0018] The invention may further include one or more of the following optional features, in any technically feasible combination: - the process includes, before step a), the arrangement of the mounting member on a support, the mounting member comprising a second face, opposite to the first face, resting on the support; - the screw heads are mounted tightly in the holes of the mounting component; - the screw heads are mounted by clipping into the holes of the mounting device; - the screw heads are mounted by shimming in the holes of the mounting device; - the mounting element comprises a number of ports between 3 and 18, and preferably between 6 and 12; - the mounting element has an angular range between 5 and 60°, and preferably on the order of 45; - the mounting element has a general polygonal cross-sectional shape, for example trapezoidal or rectangular; - the orifices of the mounting member each include a shape complementary to a screw head imprint, and in particular an imprint configured to drive the screw in rotation by means of a screwing tool; - the screw heads have a polygonal shape, and preferably hexagonal or star-shaped; and - the mounting component is made of plastic material. Brief description of the figures

[0019] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: - Fig. 1 is a schematic perspective view of a rotor disk for an aircraft turbomachine; - [Fig.2] is a partial schematic view of a radial section of a stack of two disks connected together by screws; - [Fig.3] a schematic perspective view illustrating the fixing of discs according to the prior art; - [Fig.4] a schematic perspective view of a screw mounting element according to the invention; - [Fig.5] is a schematic representation of a method for fixing discs according to the invention; - [Fig.6] is a schematic perspective representation, illustrating the placement of the fixing screws on the screw mounting element of [Fig.4] - [Fig.7] is a schematic perspective representation, illustrating the positioning of a fixing assembly consisting of the screws and the screw mounting element of [Fig.4] on the flanges of the discs, according to one embodiment; - [Fig.8] is a partial perspective section of [Fig.7]; - [Fig. 9] is a partial radial section of [Fig. 7]; and - [Fig. 10] is a schematic perspective representation, illustrating the positioning of the fixing assembly formed by the screws and the screw mounting element of [Fig. 4] on the disc flanges, according to a second embodiment. Detailed description of the invention

[0020] By convention, in the description below, the term "axial" refers to the orientation of structural elements extending along the direction of an axis. This axis corresponds substantially to an axis of rotation or revolution. The term "radial" refers to an orientation of structural elements extending in a direction perpendicular to the axis of rotation or revolution. The terms "interior," "internal," and "exterior," "external," are used with reference to a positioning relative to the axis of rotation or revolution. Thus, a structural element extending along the axis of rotation or revolution has an interior face facing the longitudinal axis and an exterior face opposite its interior face.

[0021] Figures 4 to 9 illustrate the method of fixing two discs 200a, 200b of an aircraft turbomachine according to the invention.

[0022] As mentioned above, during operation, the axis of revolution A is generally horizontal. However, for mounting or securing the discs, the discs are positioned so that the axis of revolution A is vertical, as illustrated in [Fig. 2] for example. The discs 200a, 200b are stacked or positioned one on top of the other along the axis of revolution A, which is now vertical and passes through the center of the discs 200a, 200b.

[0023] The discs 200a, 200b have radially internal annular flanges 202a, 202b, i.e., each annular flange 202a, 202b extends in a direction that is perpendicular to the axis of revolution A, while approaching this axis of revolution A. The flanges 202a, 202b, which are applied axially (i.e., along the axis of revolution A, which is vertical here) to each other, include holes 204a, 204b for receiving screws 300. These screws 300 each have a head 300a and a threaded shank 300b which passes through the holes 204a, 204b of the flanges 202a, 202b and which receives a nut 300c. Once inserted into the orifices 204a, 204b of the flanges 202a, 202b, these screws 300 are parallel to the axis of revolution A.

[0024] In order to facilitate screw tightening, the present invention proposes a screw mounting element in the orifices of the flanges 202a, 202b.

[0025] With reference to [Fig. 4], the mounting member 100 has the shape of an angular sector comprising a first face 104a which has holes 102 configured to receive the screw heads 300a. The first surface 104a is configured to bear against a face of one of the flanges

[0026] Each of the holes 102 comprises a shape complementary to the screw heads 300a. More precisely, each hole 102 is complementary to a recess in the screw heads 300a, and in particular a recess configured to rotate the screw by means of a screw-driving tool 500 such as that illustrated in [Fig. 3]. The screw heads 300a generally have a polygonal shape, and preferably a hexagonal or star shape.

[0027] The mounting member 100 may include between 3 and 18 ports. Preferably, the number of ports is between 6 and 12. The ports 102 are equidistant, with two adjacent ports 102 separated by a distance dO. The distance dO is predefined to correspond to the distance between two adjacent ports 204a, 204b of a flange 202a, 202b of a disc 200a, 200b.

[0028] The mounting member can have an angular range between 5 and 60°. Preferably the angular range is 45°.

[0029] The mounting member 100 further comprises a cross-section 106 having a generally polygonal shape. The cross-section 106 may, for example, have a trapezoidal or rectangular shape.

[0030] Preferably, the mounting member 100 is made of plastic material. It comprises, for example, polyurethane or polypropylene.

[0031] With reference to [Fig.5], the method 400 for fixing the discs 200a, 200b will now be described.

[0032] Before inserting the screws 300 into the holes 204a, 204b of the flanges 202a, 202b of the discs 200a, 200b, the flanges 202a, 202b of the discs 200a, 200b are first applied axially to each other and their holes 204a, 204b for receiving the screws 300 are aligned axially with each other 204a.

[0033] The mounting member 100 of the screws 300 is then arranged on a support Sp as illustrated in [Fig.6], the mounting member 100 comprising a second face 104b (see for example [Fig.7]), opposite to the first face 104a, resting on the support Sp.

[0034] After the mounting member 100 is placed on the support Sp, the screws 300 are put in place a) on the mounting member 100. In this step of putting in place a), the heads 300a of the screws are engaged in the holes 102, located on the first face 104a of the mounting member 100, so that the threaded rods 300b protrude from said first face 104a of the mounting member 100 and extend parallel to each other as illustrated in [Fig.6].

[0035] The screw heads 300a are mounted either by clamping, clipping, or shimming in the holes 102 of the mounting member 100. Preferably, the screw heads 300a are mounted by clamping. The mounting member 100 and the screws then form a fastening assembly EF.

[0036] Following the installation a) of the screws 300 on the mounting member 100, the fixing assembly EF, i.e. the assembly formed by the mounting member 100 and the screws 300 installed on the mounting member 100, is positioned b) on the flanges 202a, 202b of the discs 200a, 200b.

[0037] The assembly is then mounted on one side Cl of the flanges 202a, 202b, as illustrated in [Fig. 7] (i.e., the screw shanks are positioned from the holes in one of the flanges 202a, 202b), so that the threaded shanks of the screws pass through the orifices 204a, 204b of the flanges 202a, 202b until their free ends protrude from the opposite side C2 of the flanges 202a, 202b. In the example of [Fig.7], the assembly is mounted on the side of the flange 202a.

[0038] Figures 7 to 9 illustrate a first preferred method of fixing the screws 300. In this embodiment, when positioning the assembly formed by the mounting member 100 and the screws 300 on the flanges 202a, 202b, the threaded rods 300b of the screws 300 are inserted into the holes 204a, 204b of the flanges 202a, 202b from top to bottom (during assembly, the discs are positioned so that the axis of revolution A is vertical). This configuration corresponds to the case where the heads 300a of the screws 300 are mounted by compression or by clipping.

[0039] The threaded rods 300b are inserted into the orifices 204a, 204b of the flanges 202a, 202b until a portion of the first face 104a of the mounting member 100 comes to rest on a face FC1 (in the direction of the Cl side) of one of the flanges 202a, 202b as illustrated, for example, in [Fig.9].

[0040] In another embodiment of fixing the discs 200a, 200b illustrated in [Fig. 10], the shanks 300b of the screws are inserted into the holes 204a, 204b of the flanges 202a, 202b from bottom to top when positioning the assembly formed by the mounting member 100 and the screws 300. This configuration corresponds to the case where the heads 300a of the screws 300 are mounted by shimming.

[0041] Following the positioning b) of the fixing assembly EF, i.e. formed by the mounting member 100 and the screws 300 put in place, on the flanges 202a, 202b, nuts 300c are installed at the free ends of the threaded rods 300b and then screwed c) on the free ends of the threaded rods 300b of the screws 300 until they are tightened on the opposite side C2 of the flanges 202a, 202b.

[0042] Advantageously, screwing can be carried out with a single screwing tool 500, 502 and one hand, without needing to hold the screw head (unlike the prior art).

[0043] After the installation and screwing c) of the nuts 300c onto the threaded rods 300b of the screws 300, the operator first removes the screwing tool 500, 502 then, the mounting member 100 is removed d) from the heads 300a of the screws.

[0044] Thus, the risk of a collision between the screw tool 500, 502 and the disc 200a, 200b, or between the mounting member 100 and the disc 200a, 200b, can be avoided or considerably reduced. This is because the operator can manipulate the screw tool 500, 502 with one hand while fastening the discs 200a, 200b, without needing to use another screw tool 500, 502. The operator then only needs to worry about this single screw tool 500, 502. Furthermore, since the mounting member 100 is made of plastic, the risk of damage to the disc in case of the shock between the mounting element 100 and the disc 200a, 200b is considerably reduced.

[0045] The screws 300 are tightened in series, the number of screws 300 in the series being defined by the number of holes 102 in the mounting member 100. During the tightening of a series of screws 300, the mounting member 100 must remain stationary until all the screws 300 are tightened. Once the screws 300 in a series have been tightened, the operator removes d) the mounting member 100 and repositions it on a support Sp in order to install a) a new series of screws 300, and then the steps described above (positioning b) of the fastening assembly EF on the flanges 202a, 202b; installation and tightening c) of the nuts 300c and removal d) of the mounting member 100) are carried out again. The operator proceeds in this manner until all 300 screws have been fixed.

[0046] Advantageously, the mounting member 100 allows the screw heads 300a to be held securely, thus facilitating the fastening of the discs 200a, 200b. Consequently, it is no longer necessary to use two screwing tools: a first screwing tool 500 for tightening the nuts 300c and a second screwing tool 502 for holding the screw heads 300a, as illustrated in [Fig. 1]. Therefore, the operation of fastening the discs 200a, 200b is simplified for the operator, and the risk of damaging the discs 200a, 200b is avoided or considerably reduced.

[0047] In the detailed presentation of the invention given above, the terms used shall not be interpreted as limiting the invention to the embodiments set forth in this description, but shall be interpreted as including all equivalents which can be foreseen by a person skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

1. Demands A method (400) for attaching at least two discs (200a, 200b) to the rotor of an aircraft turbomachine, the discs (200a, 200b) being stacked one on top of the other (200b, 200a) along a vertical axis (A) of revolution passing through the center of said discs (200a, 200b), the discs (200a, 200b) having radially internal annular flanges (202a, 202b) that are axially applied one (200a, 200b) to the other (200b, 200a), the flanges (202a, 202b) having holes (204a, 204b) for receiving screws (300), these screws (300) being inserted into the orifices (204a, 204b) of the flanges so as to be parallel to said axis (A) of revolution, the screws (300) each having a head (300a) and a threaded shank (300b) which passes through the orifices (204a, 204b) of the flanges (202a, 202b) and which receives a nut (300c), the fastening method (400) being characterized in that it comprises the following steps: a. installation of the screws (300) on a mounting member (100) in the form of an angular sector, the mounting member (100) comprising a first face (104a) having orifices (102) of shapes complementary to the heads (300a) of screws (300), the heads (300a) of screws being engaged in these orifices (102) so that the threaded rods (300b) protrude from said face (104a) of the mounting member (100) and extend parallel to each other, the mounting member (100) and the screws (300) installed forming a fastening assembly (EF); b. The fastening assembly (EF) is positioned on the flanges (202a, 202b) of the discs (200a, 200b), the flanges (202a, 202b) of the discs (200a, 200b) having been previously axially aligned, one (202a, 202b) onto the other (202b, 202a), and their screw (300) receiving holes (204a, 204b) being axially aligned with each other. The fastening assembly (EF) is mounted on one side (Cl) of the flanges (202a, 202b) such that the threaded rods (300b) of the screws (300) pass through the holes (204a, 204b) of the flanges (202a, 202b) until their free ends protrude from the opposite side. (C2) flanges (202b, 202a); c. installation and screwing of the nuts (300c) onto the free ends of the threaded rods (300b) until they are tightened on the opposite side of the flanges (202a, 202b); and d. removal of the mounting member (100) from the screw heads (300a).

2. Method (400) of fixing according to claim 1, comprising, before step a), the arrangement of the mounting member (100) on a support (Sp), the mounting member (100) comprising a second face (104b), opposite to the first face (104a), bearing on the support (Sp).

3. A method (400) of fastening according to claim 1 or 2, wherein the heads (300a) of screws (300) are mounted tightly in the orifices (102) of the mounting member (100).

4. A method (400) of fastening according to claim 1 or 2, wherein the screw heads (300a) are mounted by clipping into the orifices (102) of the mounting member (100).

5. A method (400) of fastening according to claim 1 or 2, wherein the screw heads (300a) are mounted by wedging in the orifices (102) of the mounting member (100).

6. A method (400) of fastening according to any one of claims 1 to 5, wherein the mounting member (100) comprises a number of orifices (102) from 3 to 18, and preferably from 6 to 12.

7. A method (400) of fastening according to any one of claims 1 to 6, wherein the mounting member (100) has an angular range between 5 and 60°, and preferably of the order of 45°.

8. A method (400) of fastening according to any one of claims 1 to 7, wherein the orifices (102) of the mounting member (100) each comprise a shape complementary to an impression of the screw heads (300a), and in particular an impression configured to drive the screw (300) into rotation by means of a screwing tool (500, 502).

9. A method (400) of fastening according to any one of claims 1 to 8, wherein the screw heads (300a) have a polygonal shape, and preferably hexagonal or star-shaped.

10. A method (400) of fastening according to any one of claims 1 to 9, wherein the mounting member (100) is made of plastic material.

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