FR3118785A1 - BLOCKING PART FOR ASSEMBLY OF TURBOMACHINE ELEMENTS COMPRISING FUSE MEANS AND CORRESPONDING TURBOMACHINE - Google Patents

Abstract

TITLE: LOCKING PIECE FOR ASSEMBLY OF TURBOMACHINE ELEMENTS COMPRISING FUSE MEANS AND CORRESPONDING TURBOMACHINE engaged with a threaded fastener (6) and comprising a crimping skirt (20) configured to deform plastically, a body (21) extending the skirt (20) and anti-rotation means (26) intended to come into abutment against a rib (18) of a turbomachine element. According to the invention, the anti-rotation means (26) comprise a fusible portion (34; 37, 41) configured to break at least in part when a reaction torque exerted on the anti-rotation means (26 ), in response to a tightening or loosening torque of the fastener (6), is greater than a predetermined value. Figure for the abstract: Figure 11

Description

BLOCKING PART FOR ASSEMBLY OF TURBOMACHINE ELEMENTS COMPRISING FUSE MEANS AND CORRESPONDING TURBOMACHINE

Field of invention

The present invention relates to the field of turbomachines. It relates in particular to a blocking part intended to be mounted on a first turbomachine element in order to assemble it to a second turbomachine element. The invention also relates to a turbomachine module comprising this blocking part and the corresponding turbomachine.

Technical background

Turbomachine elements are known which are assembled together by means of an assembly device. As illustrated in Figure 1, the turbine engine comprises a first element 2 and a second element 3 each comprising a flange 2a, 3a provided with an orifice and an assembly device 4 comprising a threaded rod 4a passing through the orifices and on which is engaged a nut 4b then forming a bolted or screwed connection.

Some of the elements of the turbomachine being not very accessible during assembly, provision is made for the nut 4b to be crimped to facilitate the screwing and unscrewing of the threaded rod 4a with respect to the nut 4b. The nut indeed comprises a skirt engaged in the orifice of the flange 2a to immobilize it in translation, a body extending the skirt 4a1 and a base 4a2 extending around the body. The base comprises means forming a stop intended to come into abutment against a rib of the flange of the first element 2 so as to immobilize the nut 4b in rotation relative to the first element 2.

However, it happens for various reasons that the nut 4b and the rod 4a are seized up; the threads of the nut and the threaded rod are completely integral with each other preventing any movement between the nut and the threaded rod and thus creating the blocking of the elements of the turbomachine between them. In this situation and in particular by applying a loosening torque with specific tools, the rib has too low a mechanical resistance to stop the nut in rotation, which leads to its deterioration or even the tearing of certain portions of the rib. Such disorders can lead to the scrapping of the turbomachine element because it cannot be repaired for the most part.

Patent application FR-A1-921422 proposed to provide a sheet between the flange and the crimped nut so that the screwing and unscrewing forces of the threaded rod are transmitted to the sheet. The sheet includes a rim against which the abutment means come into abutment so as not to damage the rib of the first turbomachine element. However, when unscrewing a nut and a seized threaded rod, the unscrewing torque is transmitted only to the nut, which causes damage to the sheet. If there is no seizing and if the nut is caused to turn and comes to a stop on the edge, a small part of the torque is transmitted to the nut which is not important for severely damaging the sheet metal or the nut.

The objective of the invention is to provide an optimal solution making it possible not to damage an element of the turbomachine during a seizure phenomenon in an assembly device.

This objective is achieved in accordance with the invention by means of a blocking part for assembling two turbomachine elements, the blocking part being threaded, intended to be engaged with a threaded fixing part and comprising a crimping skirt configured to deform plastically, a body extending the skirt and anti-rotation means intended to come into abutment against a rib of a turbomachine element, the anti-rotation means comprising a fusible portion configured to break at least in part when a reaction torque exerted on the anti-rotation means, in reaction to a tightening or loosening torque of the fastener, is greater than a predetermined value.

Thus, this solution achieves the above objective. In particular, the fuse portion makes it possible to separate, at least in part, the anti-rotation means of the blocking part from the rest of its body to protect the first element in the event of seizing of a fixing part in the blocking part. This will then avoid the systematic and premature replacement of the turbomachine elements, in particular of the elements which are major parts in the operation of the turbomachine and which can be costly.

The blocking piece also includes one or more of the following features, taken alone or in combination:

- the blocking part comprises a base extending around the body and comprising the anti-rotation means.

- the anti-rotation means comprise two lugs projecting radially outwards and being opposite in a circumferential direction, the fusible portion comprising a thinned zone formed between each lug and the base.

- each lug comprises a contact surface of complementary shape with a radially inner surface of the rib.

- the fuse portion comprises an annular groove provided between the body and the base, having a depth oriented in a direction parallel to the longitudinal axis and delimited by a bottom, and a plurality of openings which pass through the bottom of the groove along the longitudinal axis.

- the edge of the sheet extends radially inside the rib and radially outside the peripheral surface of the blocking piece.

- the base includes a flat.

- the blocking piece is made of a metallic material, such as inconel®.

The invention also relates to a turbomachine module comprising a first turbomachine element, a second turbomachine element and an assembly device intended to assemble the first and second elements, the assembly device comprising a blocking part having one any of the aforementioned features and a threaded fastener engaged with the locking piece.

The turbomachinery module also includes one or more of the following features, taken alone or in combination:

- the first element comprises a flange provided with at least one orifice intended to receive the crimping skirt and the rib extending from the flange along the longitudinal axis, the base comprising a peripheral surface around the longitudinal axis and the rib being intended to be arranged radially outside the peripheral surface.

- the assembly device comprises an annular sheet having a substantially L-shaped section with an annular wall and a rim, the annular wall being intended to be formed between the flange and the blocking part, the anti-rotation means being intended to come into abutment against the rim.

- The annular wall comprises holes or indentations allowing the passage of the skirt of the blocking piece.

- the first element is a low pressure shaft and the second element is a fan shaft, the fan shaft being connected to a fan disc.

The invention also relates to a turbomachine comprising a turbomachine module as mentioned above.

The invention further relates to an aircraft comprising at least one turbomachine as mentioned above.

Brief description of figures

The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly on reading the detailed explanatory description which follows, of embodiments of the invention given as purely illustrative and non-limiting examples, with reference to the appended schematic drawings in which:

FIG. 1 represents an axial and partial section of two turbomachine elements assembled by an assembly device according to the prior art;

FIG. 2 is a schematic view, in axial and partial section, of a turbomachine module comprising a fan intended to be driven by a fan shaft according to the invention;

Figure 3 is a rear view of an embodiment of a locking part of an assembly device according to the invention;

Figure 4 is a perspective and side view of the blocking piece shown in Figure 3;

FIG. 5 illustrates in perspective another embodiment of a locking part of an assembly device according to the invention;

Figure 6 is a partial sectional view in perspective of the blocking piece according to Figure 5;

FIG. 7 is an axial and partial sectional view of an example of mounting a blocking part on a turbomachine element with a protective sheet formed between a flange of the turbomachine element and the blocking part according to FIG. invention;

FIG. 8 shows, in perspective, an example of a protective sheet intended to be installed between a first element of a turbomachine and a blocking part according to the invention;

Figure 9 is a partial perspective view of another example of a protective sheet according to the invention;

Figure 10 is a partial perspective view of another example of a protective sheet according to the invention;

FIG. 11 is a rear view in which a blocking piece is mounted on a flange of an element of a turbine engine with a protective sheet provided between the flange and the blocking piece according to the invention;

FIG. 12 is a rear view in which a blocking piece is mounted on a flange of an element of a turbine engine with another example of a protective sheet provided between the flange and the blocking piece according to the invention.

Detailed description of the invention

Figure 1 has been described above. The elements described previously and identical in the remainder of this description bear the same reference numerals.

In the present description, and in general, the terms "upstream" and "downstream" are defined with respect to the circulation of gases in the turbomachine which is substantially parallel to the longitudinal axis X. Similarly, the terms "internal" , "outer", "lower" and "upper" are defined with respect to a radial axis Z perpendicular to the longitudinal axis X and with respect to the distance from the longitudinal axis X.

FIG. 2 illustrates a turbomachine 1 comprising a first element and a second element which are assembled by an assembly device. The assembly device 4 comprises at least one blocking part 5 and at least one fixing part 6 engaged with the blocking part 5.

The turbomachine 1 shown is of the double-flow, double-body type intended to be mounted on an aircraft. The turbomachine, with a longitudinal axis X, generally comprises a fan 7 mounted upstream of a low-pressure compressor 8 following the flow of gases in the turbomachine. The fan 7 is driven in rotation by a fan shaft 9 with a longitudinal axis X and comprises a plurality of fan blades 10 which extend radially from a disc 11. This disc 11 is fixed in rotation to the fan shaft. fan 9. During its rotation, the fan 7 causes a flow which is divided into a primary flow or hot flow circulating in a primary stream 12 passing through a gas generator 13 (comprising the low pressure compressor 8) and a secondary flow or flow cold circulating in a secondary vein 14 around the gas generator 13.

The fan shaft 9 is coupled to a low pressure shaft 15 which connects the rotor of the low pressure compressor 8 and the rotor of a low pressure turbine (not shown). The low pressure shaft 15 is here the low pressure turbine shaft. Fan disk 11 is connected to low pressure compressor rotor 8 via a bolted or screwed connection. Disc 11 is also secured to fan shaft 9 by a connection, preferably bolted or screwed. This connection is made by the assembly device 4. In this case, the blocking part 5 is threaded and the fixing part 6 is threaded (with an external thread precisely). Other elements in the turbomachine can be assembled by the assembly device such as a low pressure compressor shaft and the low pressure turbine shaft forming the low pressure shaft 15.

To achieve this assembly, the disc 11 comprises an annular flange 11a which extends radially inwards (in the direction of the longitudinal axis X) and which is provided with at least one orifice 16 whose axis is parallel to the longitudinal axis X. The orifice 16 passes through the wall of the flange 11a on either side along the longitudinal axis X. The flange 11a is located at one end of an annular ferrule 11b extending from the body of the disc 11. In particular, the flange 11a comprises several orifices 16 regularly distributed around the longitudinal axis X. The fan shaft 9 also comprises an annular flange 9a which extends radially outwards (away of the longitudinal axis X) and which comprises at least one orifice 17 whose axis is parallel to the longitudinal axis X. The orifice 17 passes through the wall of the flange 9a on either side along the longitudinal axis X. Flange 9a is located at a distal end 9b of fan shaft 9 which is hollow. Several orifices 17 are regularly distributed around the longitudinal axis X. The orifices 16 and 17 are intended to coincide and to be coaxial during assembly. The fan shaft 9 also comprises a rib 18 which extends along the longitudinal axis from a downstream face 19a (visible in FIG. 7) of the flange 9a. Rib 18 is annular and substantially cylindrical. This is located near the free end of flange 9a.

The fastener 6 in the present example and illustrated in Figure 2, comprises a screw having a head extended by a threaded portion. Alternatively, the fastener includes a threaded rod (headless).

Referring to Figures 3 to 6, the first locking piece 5 comprises a crimping skirt 20 and a body 21 extending the skirt. The skirt 20 and the body 21 are cylindrical and of axis A. The locking part 5 also comprises a base 22 extending radially around the body 21.

In this example, the blocking piece 5 is a nut which is crimped onto the flange 9a. The internal threads of the nut are advantageously arranged on an internal surface 23 of the body 21. The skirt 20 is intended to be engaged in the orifice 17 as referenced in FIG. 7 to immobilize the nut in translation along the longitudinal axis. In particular, the crimping skirt 20 is configured to deform plastically. The base 22 comprises a bearing surface 24 in contact with the downstream face (into which the orifice 17 opens) of the flange 9a. The body 21 of the nut extends from this downstream face 19a of the flange 9a. Typically, the orifice 17 comprises a first cylindrical internal surface opening into the downstream face 19a (cf. FIG. 7) and a second frustoconical surface opening onto the upstream face 19b (axially opposite the downstream face) of the flange 9a. The outer diameter of the skirt 20 is substantially equal to the diameter of the first cylindrical surface of the office 16. While the inner diameter of the skirt 20 is greater than the inner diameter of the body 21. Once the skirt 20 engaged in the orifice 17 it is plastically deformed to be in contact with the frustoconical surface using suitable external tools. This allows the axial immobilization of the nut to facilitate the screwing (or tightening) and the unscrewing (or loosening) of the threaded portion or threaded rod of the fixing part 6 in the nut crimped on the flange 9a whose face downstream 19a is not accessible during assembly; the fan shaft 9 having been previously mounted in the turbomachine. The screw is engaged in hole 16 by the upstream face of the flange of disc 5.

Plastic deformation is facilitated by notches 25 which extend axially in the skirt wall 20. There are two radially opposed notches 25.

The base 22 is equipped with anti-rotation means 26 intended to come against the rib 18 of the flange 9a of the fan shaft. This prevents the nut from rotating relative to the flange when screwing or unscrewing. The anti-rotation means 26 comprise a fusible portion configured to break when a reaction torque CR is exerted on the anti-rotation means 26, in reaction to a loosening or tightening torque of the fastener 6, is greater than a predetermined value. The predetermined value corresponds, according to a first example, to 120% of the tightening or loosening torque. According to a second example, the predetermined value corresponds to 110% of the tightening or loosening torque.

This loosening torque is generally exerted by a specific external tool such as a torque wrench. Such a tool makes it possible to apply a predetermined torque for tightening or loosening the bolted connections in order to meet very specific mechanical strength criteria in the aeronautical field in particular. The loosening torque is around 100 Nm.

According to a first embodiment illustrated in Figures 3 and 4, the anti-rotation means 26 comprise two lugs 27a, 27b projecting radially outwards from the base 22. In particular, the base 22 comprises a peripheral surface 28 delimiting the base 22 and from which extend the ears 27a, 27b. More precisely still the ears 27a, 27b are opposite in a circumferential direction. Advantageously, the ears 27a, 27b are symmetrical with respect to a plane passing through the central axis A and which is vertical in the plane of FIG. 3. Each ear 27a, 27b comprises a contact surface 29 having a complementary shape with a radially inner surface of the rib 18. The planes of the contact surfaces 29 also coincide with a flat 30 of the peripheral surface 28. This flat 30 extends between the lugs 27a, 27b in the circumferential direction. Each ear 27a, 27b also comprises a lateral surface 31 defined in a plane substantially perpendicular to the plane of the contact surfaces 29. The plane is tangent to the peripheral surface 28 of the base 22. Advantageously, each ear 27a, 27b has a substantially triangular shape. The contact surfaces 29 are connected on the one hand, at a vertex 32 and on the other hand, by a base 33 (shown in dotted lines in FIG. 3).

In this example, the fusible portion comprises a thinned zone 34 which is formed between each lug 27a, 27b and the base 22. Each thinned zone 34 comprises a wall formed by a first fillet 34a and a second fillet 34b. The wall of the thinned zone 34 has a thickness which is less than the width of the base 33 of the ear 27a, 27b. Advantageously, the section reduction at the location of the thinned zone 34 is between 35% and 45%.

In this way, when the loosening torque is applied to the screw which is seized with the nut, one of the contact surfaces 29 provides a plane support connection with the radially internal surface. Indeed, the nut rotates in its hole 17 due to seizing of the screw and under the effect of the loosening torque. Under the combination of the reaction forces of the rib 18 and the loosening torque, the lug in contact with the rib finds itself stressed in flexion. In particular, the second fillet 34b works in compression while the first fillet 34a works in tension. When the reaction torque CR reaches a predetermined value, then the thinned zone breaks.

According to the embodiment illustrated in Figures 5 and 6, the blocking part 5 (nut) differs from the previous embodiment by the configuration of the anti-rotation means 26 and of the fusible portion. As shown, the base 22 comprises a transverse portion 35 which extends the base transversely with respect to the radial axis. The transverse portion 35 has a contact surface 36 having a substantially complementary shape with the radially inner surface of the rib 18 of the fan shaft. The contact surface 36 extends over an angular sector comprised between 35° and 50° and the center of which is the axis of the body of the nut. In other words, the contact surface 36 extends on either side of a plane passing through the axis A of the body of the nut. The transverse portion 35 also comprises two lateral surfaces 31' (opposite along the vertical plane passing through the axis of the body) which are each defined in a plane which is perpendicular to the plane of the contact surface 36. As for the ears, the side surface planes 31' are each tangent to the peripheral surface 28 of the base 22. The anti-rotation means 26 are formed by the transverse portion 35.

The fusible portion comprises an annular groove 37 formed, radially, between the body 21 and the base 22. The groove 37 has a U-section and is open on a downstream surface 38 of the base. The downstream surface 38 is opposite the bearing surface 24 along the longitudinal axis (axis A of the nut). Groove 38 includes a bottom 39 and two side walls 40 which extend from the bottom. The side walls are radially opposed. The depth of the groove 37 is oriented in a direction parallel to the longitudinal axis X and is delimited by the bottom 39. As can be seen in FIGS. 5 and 6, a plurality of openings 41 cross the bottom 39 of the groove of on either side along the longitudinal axis. The lights 41 are regularly distributed around the longitudinal axis. In the present example, the slots 41 each have an oblong shape, the main direction of which extends along the circumferential direction. Of course, the lights can have other shapes such as circular. The groove 37 makes it possible to thin the thickness of the base in particular along the longitudinal axis. As for the slots, these make it possible to reduce the thickness in the circumferential direction and radially.

In this way, when the loosening torque is applied to the screw which is seized with the nut, at least a part of the contact surface 36 provides a plane support connection with the radially internal surface of the rib. The nut rotates in hole 17 due to seizing of the screw and under the effect of the loosening torque. Under the combination of the reaction forces of the rib 18 and the loosening torque, the groove 37 of the nut finds itself stressed in torsion. When the reaction torque CR reaches a predetermined value, the thinned zone (groove 37 and slots 41) breaks.

In the embodiments described above, the nut can rotate without hindrance after the rupture of the fusible zone. This is enabled by the fact that the rib 18 is arranged radially outside the peripheral surface 28 of the nut.

Advantageously, the nut is made of a metallic material. Advantageously, the metallic material is an inconel®.

According to one embodiment shown in Figures 8 to 12, the assembly device 4 comprises an annular sheet 50 having a substantially L-shaped section with an annular wall 51 and a flange 52. Such a shape allows to follow the profile the flange 9a and the rib 18. The annular wall 51 is intended to be provided between the flange 9a and the locking part, here the nut. The annular wall has a complementary upstream face with the downstream face 19 of the flange 9a. The flange 52 also has a radially outer surface of complementary shape with the radially inner surface with the rib 18 as can be seen in Figure 7.

Referring to Figure 9, the sheet 50 comprises several holes 53 passing through the annular wall on either side along the longitudinal axis. The holes 53 are regularly distributed around the longitudinal axis. When installed, the holes are coaxial with port 17 of the flange. In another embodiment illustrated in Figure 10, the sheet 50 includes indentations 54 which extend radially and open onto an annular edge 55 of the sheet. The annular edge 55 is radially opposed to the edge 52. The sheet 50 is installed on the flange 9a before the crimping of the nuts. However, the diameter of the holes and the notches are greater than the diameter of each of the orifices to allow the passage of the skirt 20 of the nut. Furthermore, the base 22, and in particular the bearing surface 24, presses on the sheet 50 to hold it in position and against the flange 9a as illustrated in FIGS. 11 and 12. The dimensions of the base are greater to the diameter of the holes and notches.

The sheet is made of a metallic material. Advantageously, the metallic material comprises an inconel®. This has a thickness of between 0.1 and 1.5 mm. Advantageously, the thickness is of the order of 1 mm.

Referring to Figures 11 and 12, the anti-rotation means 26 are intended to come into abutment against the rim 52 of the sheet 60 so as to reduce the deformations of the rib 18 during the loosening or tightening torque in the event of seizure. The sheet 50 provides protection to the flange and to the rib 18 against unscrewing forces. The sheet can easily be replaced if ever it is badly damaged during unscrewing with seizing. In the event of seizure of the fixing part 6 in the nut, the loosening torque drives the anti-rotation means 26 against the rim 52 and if the reaction torque is greater than a predetermined value then the fusible portion (groove 37 or ear 27a, 27b) of the nut breaks off.

Thus, the fusible portion is arranged so as to be able to separate part of the anti-rotation means 26 (one of the lugs 27, 27b or the transverse portion 35) from the rest of the nut in the event of a reaction torque greater than a predetermined value. This separation optimally and cost-effectively protects the fan shaft rib 9 and the fan shaft itself.

Claims (11)

Blocking part (5) for assembling two turbomachine elements, the blocking part being threaded, intended to be engaged with a threaded fixing part (6) and comprising a crimping skirt (20) configured to deform plastically , a body (21) extending the skirt (20) and anti-rotation means (26) intended to come into abutment against a rib (18) of a turbomachine element, characterized in that the anti-rotation means (26 ) comprise a fusible portion (34; 37, 41) configured to break at least in part when a reaction torque exerted on the anti-rotation means (26), in reaction to a tightening torque or loosening of the fastener (6), is greater than a predetermined value. Blocking part (5) according to the preceding claim, characterized in that it comprises a base (22) extending around the body (21) and comprising the anti-rotation means (26). Blocking part (5) according to the preceding claim, characterized in that the anti-rotation means (26) comprise two lugs (27a, 27b) projecting radially outwards and being opposite in a circumferential direction, the fusible portion comprising a thinned zone (34) provided between each lug (27a, 27b) and the base (22). Blocking part (5) according to the preceding claim, characterized in that each ear (27a, 27b) comprises a contact surface (29) of complementary shape with a radially internal surface of the rib (18). Blocking piece (5) according to Claim 2, characterized in that the fuse portion comprises an annular groove (37) provided between the body (21) and the base (22), having a depth oriented in a direction parallel to the longitudinal axis and delimited by a bottom (39), and a plurality of slots (41) which pass through the bottom (39) of the groove (33) along the longitudinal axis. Turbomachine module comprising a first turbomachine element, a second turbomachine element and an assembly device (4) intended to assemble the first and second elements, the assembly device (4) comprising a blocking part (5) according any of the preceding claims and a threaded fastener (6) engaged with the locking piece (5). Turbomachine module according to the preceding claim, characterized in that the first element comprises a flange (9a) provided with at least one orifice (17) intended to receive the crimping skirt (20) and the rib (19) extending from the flange (9a) along the longitudinal axis, the base (22) comprising a peripheral surface (28) around the longitudinal axis and the rib (18) being intended to be arranged radially outside the surface peripheral. Turbomachine module according to either of Claims 6 and 7, characterized in that the assembly device (4) comprises an annular sheet (50) having a substantially L-shaped section with an annular wall (51) and a rim (52), the annular wall (51) being intended to be formed between the flange (9a) and the blocking piece (5), the anti-rotation means (26) being intended to come into abutment against the rim (52 ). Turbomachine module according to the preceding claim, characterized in that the annular wall (51) comprises holes (53) or notches (54) allowing the passage of the skirt (20) of the blocking piece (5). Turbomachine module according to any one of Claims 6 to 9, characterized in that the first element is a low-pressure shaft (15) and the second element is a fan shaft (9), the fan shaft (9) being connected to a fan disc (11). Turbomachine comprising a turbomachine module according to any one of claims 6 to 10.