Turbomachine assembly comprising an axial thrust collar for the bolted mounting of two rotor elements.

Abstract

The present disclosure relates to a turbomachine assembly comprising:- an upstream rotor element (20) comprising a downstream flange (23) and a downstream rotor element (21) comprising an upstream flange (22), the downstream flange (23) and the upstream flange (22) each having a through orifice (24);- a bolt (30) mounted in the orifices (24) of the upstream (22) and downstream (23) flanges, to fix the upstream (22) and downstream (23) flanges together, the bolt (30) comprising a screw (31);the turbomachine assembly being characterized in that it further comprises a stop ring (40) mounted on one of the upstream flange (22) and the downstream flange (23), the stop ring (40) being arranged axially opposite and at a distance from the screw (31) of the bolt (30) so as to limit an axial play of the screw (31) during assembly of the bolt (30). Abstract figure: Fig. 5

Description

Title of the invention: Turbomachine assembly comprising an axial thrust collar for the bolted mounting of two rotor elements. Technical field

[0001] The present disclosure relates to the aeronautical field. More specifically, the present disclosure relates to assemblies using a bolt in an assembly of a turbomachine, in particular at the level of the turbine disks of a turbomachine. STATE OF THE ART

[0002] Certain turbomachine parts can be assembled using bolts comprising a screw and a nut, which is particularly the case for turbine discs. Reference may be made to patent FR 3 077 327 B1 which illustrates examples of this type of assembly.

[0003] However, when the screwdriver comes into contact with the nut during tightening, the screw housed in the disc may disengage and come into contact with the projecting parts of the disc. The disc may then show wear marks caused by the impacts of the screw. The screw may also become stuck in an oblique position in the housing. The disc may then be damaged by the wear marks and / or by the screw positioned at an angle in the housing. The threaded rod of the screw may also break under the effect of the mechanical actions generated by its oblique positioning in the housing. Furthermore, the screw and the nut may be thrown against other parts of the turbomachine. In addition, the tools currently used do not allow the screw to be held satisfactorily in the event of disengagement. GENERAL STATEMENT

[0004] An aim of the present disclosure is therefore to improve the mounting of bolts in a turbomachine. Secondarily, an aim of the present disclosure is to improve the service life of the turbomachine.

[0005] To this end, according to a first aspect of the present disclosure, a turbomachine assembly is proposed comprising: - an upstream rotor element comprising a downstream flange and a downstream rotor element comprising an upstream flange, the downstream flange and the upstream flange each having a through-hole and the upstream and downstream rotor elements being centered on an axis; - a bolt mounted in the hole of the upstream flange, and in the hole of the downstream flange, to fix together the upstream flange and the downstream flange, the bolt comprising a screw; the turbomachine assembly further comprising a thrust ring mounted on one of the upstream flange and the downstream flange, the thrust ring being arranged axially in view and distance from the bolt screw so as to limit axial play of the screw when mounting the bolt.

[0006] Thus, the ferrule serves as a stop during tightening. Indeed, when it is disengaged, the screw comes into contact with the ferrule instead of coming into contact with the projecting parts of the disc. The disc is therefore protected against wear marks caused by impacts of the screw. In addition, the ferrule makes it possible to limit the movement of the screw so that it is not at an angle in the housing.

[0007] It may be provided that the stop ring is an axial stop ring.

[0008] It may be provided that the assembly further comprises a groove formed in one between the upstream flange and the downstream flange, the axial stop ring being mounted in the groove.

[0009] It may be provided that the axial stop ring is split.

[0010] It may be provided that an axial dimension of the groove is less than or equal to 2.0 mm, for example less than or equal to 1.5 mm, typically less than or equal to 1.0 mm.

[0011] It may be provided that a ratio between a radial dimension of the groove and a radial dimension of the axial stop ring is between 0.5 and 0.7.

[0012] It may be provided that the screw has a head comprising a portion of constant radius, a minimum axial dimension of the portion of the head being greater than or equal to 3.0 mm, for example greater than or equal to 3.5 mm, typically greater than or equal to 4.0 mm.

[0013] It may be provided that the screw comprises a head whose section is non-circular and configured to come into abutment against one of the upstream flange and the downstream flange.

[0014] It may be provided that the axial stop ring comprises at least one lug.

[0015] It may be provided that the lug is arranged on the axial stop ring so as to prevent rotation of the axial thrust ring around the axis and / or to limit unbalance of the turbomachine assembly.

[0016] According to a second aspect of the present disclosure, there is provided a turbine, for example low pressure, comprising: - a turbomachine assembly according to the first aspect; and - a sealing ferrule mounted axially between the upstream flange and the downstream flange.

[0017] According to a third aspect of the present disclosure, there is provided an aircraft turbomachine comprising: - a turbomachine assembly according to the first aspect; and - a casing coaxial with the assembly.

[0018] According to a fourth aspect of the present disclosure, there is provided an aircraft comprising a pylon and an aircraft turbomachine according to the third aspect, the turbomachine being connected to the pylon.

[0019] According to a fifth aspect of the present disclosure, there is proposed a method of mounting a turbomachine assembly according to the first aspect comprising the following steps: - insertion of a screw into the through hole of the upstream flange and the downstream flange; - mounting the stop ring axially opposite and at a distance from the screw on one of the upstream flange and the downstream flange; and - tightening the bolt. DESCRIPTION OF FIGURES

[0020] Other characteristics, aims and advantages will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0021] [Fig.l] is a schematic view from above of an aircraft;

[0022] [Fig.2] is a schematic half-sectional view of a turbomachine;

[0023] [Fig.3] is a schematic sectional view of a low pressure turbine disc;

[0024] [Fig.4] is a schematic sectional view of a low pressure turbine;

[0025] [Fig.5] is a close-up view of [Fig.4];

[0026] [Fig.6a] is a close-up view of [Fig.5];

[0027] [Fig.6b] is a schematic perspective view of a ferrule;

[0028] [Fig.7a] is a close-up view of [Fig.5] according to another embodiment;

[0029] [Fig.7b] is a schematic perspective view of a lug; and

[0030] [Fig.8] is a flowchart of a method of implementing a method assembly of a turbomachine assembly. DETAILED DESCRIPTION

[0031] An aircraft 1 is a device configured to rise and move in the air, and may, for example, be an airplane, civil or military, or even a helicopter. According to an example in [Fig.l] illustrating an aircraft 1 in the case of an airplane, the aircraft 1 comprises a cell 10 which has a fuselage and two wings and landing gear. The aircraft 1 further comprises a propulsion system 100 in order to give it the thrust necessary for its rise and movement in the air. Of course, the aircraft 1 may comprise a plurality of propulsion systems 100, for example one propulsion system 100 per wing according to the aircraft 1 illustrated as an example in [Fig.l].

[0032] Unless otherwise specified, the terms "upstream" and "downstream" are used in reference to the overall direction of airflow through the propulsion system 100 in operation.

[0033] The propulsion system 100 comprises a turbomachine 110 configured to be fixed to the cell 10 of the aircraft 1, for example to the wings, in the case of the aircraft in [Fig.l], typically by means of a pylon (or mast). The turbomachine 110 can also be mounted at the rear of the fuselage, or even be integrated into the fuselage of the aircraft 1. The turbomachine 110 comprises a gas generator 120 configured to provide propulsion for the aircraft 1. The gas generator 120 comprises from upstream to downstream a compression section 121, a combustion chamber 122, a turbine section 123 and a primary nozzle 124. The compression section 121 comprises a plurality of stages each comprising a moving wheel 1212 and a stator portion 1213 (or rectifier). Each turbine section 123 comprises a plurality of stages each comprising a moving wheel 1232 and a stator portion 1233 (or distributor).The gas generator 120 may be single-spool, i.e. the gas generator 120 comprises a single shaft mechanically connected to the compressor section 121 and the turbine section 123, or multi-spool, i.e. the gas generator comprises a plurality of shafts, each shaft being mechanically connected to a finite number of stages of the compression 121 and turbine 123 sections. The turbomachine 110 may further comprise a fan 130, mechanically connected to the gas generator 120 by direct drive or by interposition of a reduction stage. The fan 130 may be shrouded, i.e. it is housed in a retention casing 140, or unshrouded, i.e. it is not housed in a retention casing and is in the form of propellers. Thus, the turbomachine 110 may comprise a different number of bodies and / or flows. It may be a turbojet, a turboprop or a turboshaft engine.

[0034] An example of a turbomachine 110 is illustrated in [Fig.2]. In this example, the turbomachine comprises, from upstream to downstream in the direction of flow of the gases A, a ducted fan 130 housed in a retention casing 140, and a gas generator 120 comprising a compression section 121 comprising a low-pressure compressor 1210 and a high-pressure compressor 1211, a combustion chamber 122, a turbine section 123 comprising a high-pressure turbine 1230 and a low-pressure turbine 1231, and a primary nozzle 124. In this case, the gas generator 120 is a double-body type and comprises a high-pressure shaft 125 which is connected to the high-pressure turbine 1230 and to the high-pressure compressor 1211, and a low-pressure shaft 126 which is connected to the low-pressure turbine 1231, to the low-pressure compressor 1210 and to the fan 130.Each compression section 121 comprises a plurality of stages each comprising a movable wheel 1212 and a rectifier 1213. Each turbine section 123 comprises a plurality of stages each comprising a movable wheel 1232 and a distributor 1233. The air flow A entering the turbomachine 110 following the suction generated by the fan 130 is divided into a primary flow A1 configured to pass through the gas generator 120 and a secondary flow A2 which bypasses the gas generator 120, most of the thrust generated by the turbomachine 110 being linked to the secondary flow A2 in . this configuration.

[0035] An upstream rotor element 20 of the turbomachine 110 comprises a downstream flange 23 and a downstream rotor element 21 of the turbomachine comprises an upstream flange 22. In addition, the upstream 22 and downstream 23 flanges each have a through orifice 24. The rotating elements 20, 21 may be, for example, moving wheels of the compression section 121 and / or of the turbine section 123 or of any other member of the turbomachine 110 comprising a hub that can rotate.

[0036] The upstream rotor element 20 is rotatable about a longitudinal axis X. An axial direction corresponds to a direction collinear with the longitudinal axis X and a radial direction is a direction orthogonal to the longitudinal axis X and intersecting the longitudinal axis X. Furthermore, an axial plane is a plane parallel to the longitudinal axis X and a radial plane is a plane orthogonal to the longitudinal axis X. A circumference is understood to be a circle belonging to a radial plane and whose center belongs to the longitudinal axis X. A tangential or circumferential direction is a direction tangent to a circumference: it is orthogonal to the longitudinal axis X but does not pass through the longitudinal axis X. A circumferential plane is a plane normal to a radial axis, the radial axis being perpendicular to the longitudinal axis X.Finally, the adjectives "inner" (or "internal") and "outer" (or "external") are used in reference to a radial direction so that the inner part of an element is, in a radial direction, closer to the longitudinal axis X than the outer part of the same element.

[0037] An example of a downstream rotor element 21 is illustrated in [Fig. 3]. This is not, however, limiting, the present description being able to be applied to any rotor element of the turbomachine 110.

[0038] In this example, the downstream rotor element 21 is a low-pressure turbine disk 1231 extending in a circumferential direction. The disk 21 includes a web 25 extending in a radial direction and opposing flanges 22, 23 each extending in an axial direction. A rim 251 extends over a radially outer portion of the web 25 and a bore 250 extends over a radially inner portion of the web 25. Cells 26 are formed on a radially outer portion of the rim 251 and are configured to receive rotor blades of the low-pressure turbine 1231. A crown 27 is formed on each end of the flanges 22, 23 and includes through-holes 24. The crown 27 may extend over an entire circumference of the disk 21 or a portion thereof. A distance between two adjacent orifices 24 of the crown 27 may be variable or identical.

[0039] A casing of the turbomachine is centered on the rotating elements 20, 21. The casing may be the retention casing 140 of the fan 130. It may also be one of the following casings: - a rectifier 1213 of the compression section 121; - a distributor 1233 of the turbine section 123; - an inter-turbine casing configured to extend into the turbine section 123; or - an exhaust casing extending downstream of the turbine section 123.

[0040] A bolt 30 is mounted in the orifice 24 of each of the upstream 22 and downstream 23 flanges so as to connect the upstream flange 22 and the downstream flange 23 (as illustrated for example in [Fig.4]). The bolt 30 comprises a screw 31 and a nut 32. The screw 31 comprises a threaded rod 310 passing through the orifice 24 of the upstream flange 22 and the downstream flange 23 and a head 311, integral with the threaded rod 310. In a first mounting direction, the head 311 is against a first face 270 extending in a radial plane passing through the upstream flange 22, the upstream flange 22 comprising the first face 270 and the orifice 24 of the upstream flange 22 passing through the first face 270. In a second mounting direction, the head 311 is against a second face 271 extending in a radial plane passing through the downstream flange 23, the downstream flange 23 comprising the second face 271 and the orifice 24 of the downstream flange 23 passing through the second face 271.In order for the screw 31 to be stopped in rotation when the bolt 30 is tightened, the head 311 may comprise a non-circular section configured to come into abutment against the upstream flange 22, in the first mounting direction, and the downstream flange 23, in the second mounting direction. The non-circular section is here defined in a circumferential plane passing through one end of the head 311. The non-circular section may be a quadrilateral, for example a square or a rectangle. The nut 32 screwed onto the threaded rod 310 is in contact against the second face 271, in the first mounting direction, and against the first face 270, in the second mounting direction. The rotating elements 20, 21 may be in direct contact or reciprocally against an intermediate part 70, for example a seal.

[0041] In the following, the present disclosure will be detailed for the first mounting direction and applies mutatis mutandis to the second mounting direction.

[0042] In order to avoid the use of tools currently in use, a ferrule 40 is mounted on the upstream flange 22 of the downstream rotor element 21, for example by fitting into the upstream flange 22, or even by bolted assembly using a bolt separate from the bolt 30 connecting the upstream 22 and downstream 23 flanges. The ferrule 40 is configured to extend axially opposite and at a distance from the screw 31 of the bolt 30 so as to limit axial play of the screw 31 in the orifice 24 during assembly. Thus, in the event of disengagement of the screw 31 during assembly, the screw 31 is then in contact against a part of the ferrule 40 extending axially opposite and at a distance from the screw 31. There is therefore no risk of disengagement of the screw 31. There is also no risk of the screw 31 being at an angle in the orifice 22. Consequently, the ferrule 40 prevents the screw 31 from damaging the rotating elements 20, 21.Thus, the service life of the downstream rotor element 21, and consequently the service life of the turbomachine 110, are increased. In addition, the shell . 40 is a means of limiting the axial play of the screw 31 in the hole when mounted on the upstream flange 22 securely and with minimal modification to the downstream rotor element 21. The ferrule 40 extends a maximum distance from the head 311 such that the screw 31 does not come into contact with protruding portions of the upstream rotor element and remains straight in the event of disengagement. For example, the maximum distance may be between 0.1 mm and 1 mm when a length of a diagonal of the head 311 is equal to 3 mm.

[0043] The ferrule 40 may be monolithic or in several parts which may be in one piece or separate from each other.

[0044] According to a first exemplary embodiment, the ferrule 40 comprises a ring extending around the axis X. The ring comprises, in an axial plane passing through the ring, a rectangular section.

[0045] Alternatively, the ring may comprise, in the axial plane passing through the ring, a square or circular section (in the case of a “torus”).

[0046] According to a second embodiment, the ferrule 40 may comprise ring sectors arranged circumferentially around the axis X.

[0047] The ferrule 40 can be mounted in a groove 28 formed in the upstream flange 22, for example by fitting into the groove 28, or even by bolted assembly using a bolt separate from the bolt 30 connecting the upstream 22 and downstream 23 flanges.

[0048] According to one embodiment, the groove 28 extends around the axis X. The groove 28 is formed on a radially internal face 220 of the upstream flange 22 of substantially cylindrical shape (as illustrated for example in FIGS. 5 and 6a). The groove comprises a bottom 281, in a radially external position relative to the radially internal face 220 of the upstream flange 22, so that the groove 28 extends in the radial direction between the radially internal face 220 of the upstream flange 22 and the bottom 281. Furthermore, the bottom 281 has a substantially cylindrical shape. The groove 28 also comprises an upstream face 282 and a downstream face 283 opposite the upstream face 282, so that the groove 28 extends in the axial direction between the two upstream faces 282 and downstream 283 of the groove 28. Therefore, the groove 28 forms an annular cavity in which the ferrule 40 can be housed.

[0049] In variants, the radially internal face 220 of the upstream flange 22 may have a substantially conical shape. The bottom 281 may have a substantially conical shape. The groove 28 may extend over several distinct portions around the axis X. In an axial plane passing through the groove 28, the upstream face 282, respectively downstream face 283, may, from upstream to downstream, move away from or towards the axis. Of course, the variants may be taken alone or in combination.

[0050] The ferrule 40 can also be split and force-fitted into the groove 28. The force-fitting has the advantage of holding the ferrule 40 even more firmly in the groove 28, in particular by making use of a centrifugal effect generated by a rotation of the downstream rotor element 21 during operation of the turbomachine 110.

[0051] According to one embodiment, the ferrule 40 comprises the ring previously described. The ring further comprises a radial slot on an annular portion (illustrated for example in [Fig.6b]). The radial slot extends from an inner end of the ring to an outer end of the ring. The radial slot is configured to vary a diameter of the ring so as to forcefully mount the ring in the groove 28. Indeed, by applying a force to the ring, two opposite faces of the radial slot move closer together in order to insert the ring into the groove 28 and then move away to maintain the ring in position in the groove 28 when the force on the ring is released. Therefore, in this embodiment, the ring has, in a free state, an external diameter greater than an external diameter of the groove 28. For example, an external diameter of the ring is equal to 500.1 mm and an external diameter of the groove 28 is equal to 500 mm.

[0052] In order to avoid significantly modifying a mass of the turbomachine 110, a minimum axial dimension L2 of the groove 28 between an upstream face 282 and a downstream face 283 of the groove 28, measured in an axial plane passing through the groove 28, may be less than or equal to 1 mm, for example less than or equal to 1.5 mm, typically less than or equal to 2 mm. In order to limit a deformation of the ring caused by contact of the head 311 against the ferrule 40 during assembly, a ratio between a minimum radial dimension L3 of the groove 28 between the bottom of the groove 281 and the radially internal face 220 of the upstream flange 22 of the downstream rotor element 21, measured in a radial plane passing through the groove 28 and the ferrule 40, and a maximum radial dimension L4 of the ferrule 40 between an internal end 44 of the ferrule 40 and an external end 46 of the ferrule 40, measured in a radial plane passing through the groove 28 and the ferrule 40, may be between 0.5 and 0.7.In this case, the minimum radial dimension L3 of the groove 28 may be between 2 mm and 4 mm, preferably between 2.5 mm and 3.5 mm, and the radial dimension L4 of the ferrule 40 may be between 4 mm and 6 mm, preferably between 4.5 mm and 5.5 mm. When the ferrule 40 is annular, the radial dimension L4 of the ferrule 40 therefore corresponds to a difference between an internal radius RI and an external radius R2 of the ferrule 40. An example of an internal radius RI and an external radius R2 is illustrated in [Fig.6b]. In order to prevent the head 311 from plasticizing when it comes into contact with the ferrule 40 during assembly, the head 311 comprises a first frustoconical portion 312 and a second portion 313 of constant radius, a minimum axial dimension L7 of which, taken in an axial plane passing through the portion, is greater than 1 mm. In order to maintain the mechanical performance of the downstream rotor element 21, a minimum axial dimension L8 between the downstream face of the . groove 283 and a downstream face 221 of the upstream flange 22 opposite the downstream face of the groove 283, measured in an axial plane passing through the upstream flange, is greater than 1 mm.

[0053] Other preferred dimensional characteristics of the ferrule 40 and / or the groove 28 which may be taken alone or in combination are also listed below: - an axial dimension L1 of the upstream flange 22, between the first face 270 of the upstream flange 22 and the upstream face 282 of the groove 28, measured in an axial plane passing through the upstream flange 22, may be between 3 mm and 5 mm, preferably between 3.5 mm and 4.5 mm; - a radial dimension L5 between a radially external end of the head 311 and a radially internal end of the ferrule 40, taken in an axial plane passing through the head 311 and the ferrule 40, may be between 0.4 mm and 1.6 mm, preferably between 0.5 mm and 1.5 mm; - an axial dimension of the ferrule L6 between an upstream face 41 and a downstream face 43 of the ferrule 40, measured in an axial plane passing through the ferrule 40, may be between 0.24 mm and 0.46 mm, preferably between 0.25 mm and 0.45 mm.

[0054] To achieve dynamic balancing and static balancing of the turbomachine 110, the shell 40 may also comprise a lug 42 mounted on the shell 40 and configured to modify an unbalance of the turbomachine 110. For example, in a radial plane passing through the shell 40, the lug 42 is at a position opposite a position of a point of application of a resultant of the unbalance.

[0055] The lug 42 may further be configured to prevent rotation of the ferrule 40 around the X axis so as not to shift the position of the lug 42 relative to the position of the point of application of the resultant of the unbalance.

[0056] According to an exemplary embodiment, the lug 42 is in contact with the head 311 of the screw 31 so that the lug 42 prevents the rotation of the ring 40 around the axis X.

[0057] The lug 42 can be monolithic with the ferrule 40 or assembled to the ferrule 40.

[0058] According to a first embodiment, the lug 42 comprises a tooth (illustrated by examples in FIGS. 7a and 7b) extending in projection from an upstream face 41 of the ferrule 40 and monolithic with the ferrule 40. The tooth comprises, in an axial plane passing through the ferrule 40, a rectangular section.

[0059] According to a second embodiment, the lug 42 may be a weight assembled to the ferrule 40 by a bolt separate from the bolt 30 for assembling the upstream 20 and downstream 21 rotating elements or by interlocking.

[0060] According to a third embodiment, the lug 42 may comprise a bolt for mounting the ferrule 40 in the groove 28.

[0061] A thickness of the lug 42, the thickness extending between two ends of the lug 42 in a radial plane passing through the lug 42, can be determined as a function of the dynamic balancing and the static balancing of the turbomachine 110 to be carried out. A width of the lug 42, the width extending in a circumferential plane passing through the lug 42, can be determined as a function of the dynamic balancing and the static balancing of the turbomachine 110 to be carried out. A length of the lug 42, the length extending between an upstream end and a downstream end of the lug 42, can be determined as a function of the dynamic balancing and the static balancing of the turbomachine 110 to be carried out.

[0062] Of course, the ferrule 40 may comprise a single lug 42 or a plurality of lugs 42. Furthermore, all the characteristics described for the lug 42 may be taken alone or in combination for one, several or all of the pins of the plurality of lugs.

[0063] In order to assemble the moving parts of the turbomachine 110, in particular the moving parts of the low-pressure turbine 1231, an assembly method is proposed in which, with reference to [Fig.8], the following steps are implemented.

[0064] During a step E1, the screw 31 is inserted into the through-orifice 24 of the upstream flange 22 of the downstream rotor element 21 and of the downstream flange 23 of the upstream rotor element 20. The screw 31 can be inserted in a direction opposite to the direction of the primary flow A1. Thus, the assembly of the upstream and downstream rotating elements 21, 22 is done “vertically” in order to prevent the screw 31 from falling by gravity during assembly.

[0065] During a step E2, the ferrule 40 is mounted axially opposite and at a distance from the screw 31 on the upstream flange 22.

[0066] During a step E3 the bolt 30 is tightened.

[0067] Many modifications can be made without departing from the scope of this presentation.

Claims

Claims

1. A turbomachine assembly comprising: - an upstream rotor element (20) comprising a downstream flange (23) and a downstream rotor element (21) comprising an upstream flange (22), the downstream flange (23) and the upstream flange (22) each having a through orifice (24) and the upstream and downstream rotor elements (20, 21) being centered on an axis (X); - a bolt (30) mounted in the orifice (24) of the upstream flange (22), and in the orifice (24) of the downstream flange (23), for fixing together the upstream flange (22) and the downstream flange (23), the bolt (30) comprising a screw (31); the turbomachine assembly being characterized in that it further comprises a stop ring (40) mounted on one of the upstream flange (22) and the downstream flange (23), the stop ring (40) being arranged axially opposite and at a distance from the screw (31) of the bolt (30) so as to limit axial play of the screw (31) during mounting of the bolt (30).

2. An assembly according to claim 1, wherein the stop ring (40) is an axial stop ring.

3. An assembly according to claim 2, further comprising a groove (28) formed in one of the upstream flange (22) and the downstream flange (23), the axial stop ring (40) being mounted in the groove (28).

4. An assembly according to claim 3, wherein the axial stop ring (40) is split.

5. Assembly according to one of claims 3 to 4, in which an axial dimension (L2) of the groove (28) is less than or equal to 2.0 mm, for example less than or equal to 1.5 mm, typically less than or equal to 1.0 mm.

6. Assembly according to one of claims 3 to 5, in which a ratio between a radial dimension (L3) of the groove (28) and a radial dimension (L4) of the axial stop ring (40) is between 0.5 and 0.

7.

7. Assembly according to one of claims 1 to 6, in which the screw (31) has a head (311) comprising a portion of constant radius, a minimum axial dimension (L7) of the portion of the head (311) being greater than or equal to 3.0 mm, for example greater than or equal to 3.5 mm, typically greater than or equal to 4.0 mm.

8. Assembly according to one of claims 1 to 7, in which the screw (31) comprises a head (311) of which a section is non-circular and configured to abut against one of the upstream flange (22) and the downstream flange (23).

9. Assembly according to one of claims 2 to 8, in which the axial stop ring (40) comprises at least one lug (42).

10. An assembly according to claim 9, wherein the lug (42) is arranged on the axial stop ring (40) so as to prevent rotation of the axial stop ring (40) around the axis (X) and / or to limit an imbalance of the turbomachine assembly.

11. Turbine (123), for example low pressure (1231), comprising: - a turbomachine assembly according to one of claims 1 to 10; and - a sealing shroud (70) mounted axially between the upstream flange (22) and the downstream flange (23).

12. Aircraft turbomachine (110) comprising: - a turbomachine assembly according to one of claims 1 to 10; and - a casing coaxial with the assembly.

13. Method for mounting a turbomachine assembly according to one of claims 1 to 10 comprising the following steps: - insertion (El) of a screw (31) into the orifice (24) passing through the upstream flange (22) and the downstream flange (23); - mounting (E2) of the stop ring (40) axially opposite and at a distance from the screw (31) on one of the upstream flange (22) and the downstream flange (23); and - tightening (E3) of the bolt (30).

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