FR3039857B1 - METHOD AND DEVICE FOR CLAMPING A ROTOR LINE OF TURBOMACHINE - Google Patents

Abstract

The invention relates to a method for clamping a turbomachine rotor line (7) composed of a succession of elements (7a, 7b) contiguous along an axis (X), comprising inserting along said axis (X ) an elongated tie rod (10) at the center of said elements for bringing a first end of said tie rod into axial abutment against a portion (16) of a first axial end (B) of the rotor line (7), the second end of the tie rod ( 10) located at the second axial end (A) of the rotor line (7), characterized in that it also comprises increasing the length (L) of the tie rod (10) by a value ( A), the fact of installing a lock (24) on the second end of the tie rod (10) by a dog-type connection, and allowing the tie rod to return to its initial length, so that a part (28b) of said latch (24) bears on a portion (15) of the second end (A) of the rotor line (7), in the opposite direction to the stop on the first end (B). The invention also relates to the associated device.

Description

Method and device for clamping a turbomachine rotor line

TECHNICAL FIELD The invention relates to turbomachine rotors and more particularly to the means for holding the on-line assembly of successive disks forming these rotors.

State of the art :

Rotors of compressors or turbines in turbomachines for aeronautics generally comprise several successive stages of blades attached to discs. These stages are manufactured separately and the disks are assembled to form a rotor line rotating a shaft of the turbomachine.

The coupling between two successive elements of the rotor line is generally performed by connecting members which cooperate by rows of circumferential teeth, oriented along the axis and having curvilinear profiles arranged so that the teeth fit into each other . Such a coupling system by interlocking teeth with curved profiles is usually referred to as the Anglo-Saxon term "curvic coupling" ("coupling with curved or trapezoidal teeth"). On the one hand, the adjustment of the nested teeth in each other makes it possible to transmit the torques between the different elements of the rotor line. On the other hand, this mode of coupling makes it possible to manufacture the elements separately and then to assemble them easily by positioning them precisely with respect to each other.

However, coupling the elements by interlocking teeth requires axial clamping of the rotor line to prevent play between the elements, or even their uncoupling. This can degrade the operation of the turbomachine, cause premature wear of the elements and even cause a departure in overspeed of the rotor. The problem can be particularly severe in the turbine of the high pressure body where efforts are important.

It is known, for effecting the clamping of the high pressure rotor line, to use a tie rod, for example a hollow rod which passes in the center of the disks of the elements of the rotor line and retains the elements of the rotor line between axial stops. at each of its ends, and screw nuts on the tie rod to apply axial pressure between said stops.

In analyzing cases of breakdowns, it has appeared, in particular for the rotors of the high pressure body of the turbomachines, that the tightening forces by the tie rod must be very high in order to maintain the cohesion of the discs and that these efforts may cause the threads to break. tightening nuts on the tie rod. A modification of material has been envisaged to increase the value of permissible stress, but the gains that can be obtained with accessible materials are insufficient to allow the mechanical strength of the threads to the forces induced by the necessary tightening. The object of the invention is to propose a solution to the problem of tightening a rotor line subjected to high forces, which is economical, reliable and makes it possible to maintain an assembly of the elements of the line with the current techniques of interlocking coupling. teeth, called "curvic coupling".

PRESENTATION OF THE INVENTION The invention relates for this purpose to a method of clamping a turbomachine rotor line composed of at least two elements contiguous along an axis, in particular of rotation of the rotor, comprising a subsequent insertion step. said axis of an elongated tie rod substantially in the center of said elements for bringing a first longitudinal end of the tie rod into axial abutment against a first axial end of the rotor line, the tie rod having a given length in a first state such as a second longitudinal end of the tie is substantially at a second axial end of the rotor line, opposite said first axial end.

The method is remarkable in that it also comprises steps of: - submitting the puller to constraints to bring said tie rod into a second state in which its length is increased by a given value, - mounting a lock on the longitudinal end of the tie rod by a dog-type connection, when the tie rod is under stress, in the second state, and abutting against the first axial end of the rotor line, and - releasing the stresses of the tie rod, so as to leave it returning to a third state, in which its length takes an intermediate value between those of the first and second state and stop means of said latch press on a part of the second axial end of the rotor line, so as to tighten the rotor line between its two longitudinal ends along the axis.

Returning from the second state to the third state, the tie retracts and exerts a compressive force substantially proportional to the difference in length that will have been provided between the distance that would exist between the stop of the lock and its first longitudinal end, if it were free , and the distance that actually exists between these stops when the tie rod is installed in the rotor line. Advantageously, the clamping force exerted by the tie rod on the rotor line can thus be adjusted by adjusting this difference in distance.

Furthermore, the fact of using a jaw-like type of connection between the latch and the tie rod makes it possible to have teeth that support high compressive forces, and therefore to adjust the tightening to the level required for rotor lines of the high pressure body, for example. example. The lengthening of the tie rod makes it possible to install this dog link before allowing it to retract. On the one hand, it is not necessary to use the connection between the latch and the tie rod to put the tie rod in tension as in the case of a thread connection, on the other hand, the teeth of the dog link withstand higher pressures than threads.

Preferably, the passage of the pulling of the first state to the second state is done by subjecting it to a traction directed along the axis at its second longitudinal end.

In this case, the tie rod being made in its elongated portion in a given elastic modulus material, the elongation of the tie is advantageously remaining in the field of elastic deformations of the elongated portion. One can thus maintain a substantially proportional relationship between the elongation of the tie rod and the clamping force applied. The invention also relates to a device for implementing the method described above, comprising an elongated tie rod and a latch, the tie rod comprising first means installed on a first longitudinal end of the tie rod and forming a longitudinal stop facing towards a second longitudinal end, opposite to the first longitudinal end, characterized in that the second longitudinal end of the tie rod comprises a first circumferential succession of teeth arranged to cooperate with a second circumferential succession of teeth arranged on the latch, to form a type of connection. dog clutch longitudinally locking the lock in the direction from the first longitudinal end to the second, and in that the lock comprises second means arranged to form, when the dog-type connection is made, a second longitudinal stop facing towards the first longitudinal end of the tie rod.

With such a device, the length of which has been previously chosen to correspond to the first state of said method, the method can be applied and the lock can be installed on the tie rod when the latter is in the second state of the process and is in abutment on the first end of the rotor line.

Advantageously, at least one of the teeth of one of the circumferential succession of teeth comprises first circumferential abutment means arranged at a first circumferential end of a face serving as a support for the dog-type connection and extending longitudinally. from said face.

This makes it possible to install the teeth of the lock facing those of the head of the tie by relying on the circumferential stop.

Preferably, said at least one tooth comprises second circumferential abutment means disposed at the second circumferential end of said face serving as a support for the dog-type connection and extending longitudinally from said face for a distance less than that said first circumferential abutment means.

The second means make it possible to maintain in a secure manner the interconnection link when the turbomachine is in operation.

Preferably, the tie rod has a hollow tubular shape.

Advantageously, the tie has a thickening substantially to the right of the circumferential succession of teeth participating in the link type dog.

Advantageously, the extra thickness comprises a portion arranged to cooperate with a traction tool or tension. The invention also relates to a turbomachine assembly comprising a rotor line formed of at least two elements contiguous along an axis and a device as described above, said assembly being arranged such that: said elements of the rotor line are arranged to be traversed along the axis by the tie rod, - a first axial stop is disposed on a first axial end of the rotor line so as to cooperate with the first longitudinal stop means of the tie rod, - a second axial stop is arranged on the second axial end of the rotor line so as to cooperate with the second longitudinal stop means disposed on the lock, and - said tie rod passing through the rotor line along the axis, the first longitudinal stop means of the tie rod bear against the abutment of the first axial end of the rotor line and the lock is installed on the tie rod by the connection type crabo t, being in axial bearing in one direction against the tie rod and in the opposite direction against the axial stop of the second axial end of the rotor line. The invention also relates to a turbomachine comprising such a turbomachine assembly.

Brief description of the drawings:

The present invention will be better understood and other details, features and advantages of the present invention will become more apparent upon reading the following description with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic half-section of an example of a turbomachine using a device according to the invention.

Figure 2 shows schematically, viewed from the side along the axis, a tie according to the invention placed in a rotor line.

Figures 3a and 3b schematically shows a tie rod according to the invention, seen from the side and in longitudinal half-section.

Figure 4 shows a perspective view of a detail of the end of the tie rod according to the invention for cooperating with a lock.

FIG. 5 presents a perspective view of a lock according to the invention intended to cooperate with the part of the tie rod of FIG. 4.

Figure 6 shows the path followed by the lock on the tie rod of Figure 4 to achieve a jaw type link according to the invention.

Parts a) -d) of Figure 7 show the main steps of a method of clamping a rotor line according to the invention.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION The invention relates to the clamping of rotor lines in a turbomachine which can correspond to that shown in FIG. 1. In the example shown, it is a turbomachine double flow comprising in particular, for the motor part, a low pressure compressor 1, a high pressure compressor 2, a combustion chamber 3, a high pressure turbine 4 and a low pressure turbine 5, and for the part driving the secondary flow, a blower 6.

The high-pressure compressor 2, the combustion chamber 3 and the high-pressure turbine 4 form the high-pressure body of the turbomachine. In this example, the rotor of the high-pressure turbine 4 comprises several disks 7, equipped with vanes and interposed axially between stator stages 8. The disks 7 of the rotor of the high-pressure turbine 4 rotate together at the same speed, and drive, by the shaft 9 of the high pressure body, the rotor of the high pressure compressor 2.

During the manufacture of the turbomachine, the discs 7 of the rotor of the high-pressure turbine 4 are generally assembled successively between the stator stages 8 and then secured by an axial clamping process in order to be connected to the shaft 9 of the body high pressure.

Referring to Figure 2, the axial clamping of the discs 7 of the rotor line is effected by means of a tie rod 10 passing through a free circular space at the center of the discs, along the axis X of rotation.

The rotor line is between a first axial end B and a second axial end A. For reasons of convenience in the rest of the description, the axis X of the rotor line and the tie rod 10 is oriented here so as to define a direction downstream, going from the first end B to the second end A of the rotor line, and a direction upstream opposite. The arrow of the X axis in the figure therefore indicates the downstream direction. The concepts of upstream and downstream are therefore not necessarily associated with the direction of flow of a fluid, nor with the orientation with respect to the turbomachine.

In Figure 2, only two disks 7a, 7b, located at the second axial end A of the rotor line are shown. Each disc 7a, 7b comprises a main body 11 forming a ring whose outer periphery supports the blades, not shown, and the inner periphery leaves a circular space, whose diameter is at least equal to a minimum diameter OD, thus allowing the passage of the shaft 9, not shown, and the tie rod 10.

As shown in Figure 2, two successive disks 7a, 7b each comprise a ferrule 12 connected to the main body 11, substantially cylindrical and facing the other disk. The free ends of these ferrules 12 each comprise the complementary members 13 of a coupling coupling coupling coupling, called "curvic coupling", as presented in the introduction. The rings 12 are arranged such that these members 13 cooperate when the discs 7a, 7b are pressed axially against each other, so as to secure in rotation the assembly of the rotor line.

The disc 7a placed at the second end A comprises a trunnion 14 of tubular shape extending axially downstream. The inner section of the trunnion 14 has a diameter at least equal to said minimum diameter OD but has on its radially inner periphery a ring of internal diameter DI which is lower and has a transverse face 15 facing downstream, so as to form an axial stop towards the upstream of the rotor line for a body in translation along the axis X.

The first axial end B of the rotor line is not explicitly shown in FIG. 2, but the disk 7b can represent the disk that would be placed at this first end B. In particular, the disk placed at the first end B generally has a transverse surface 16, having a substantially circular inner periphery of diameter D2 at least equal to said minimum diameter OD, facing upstream and arranged to form an axial abutment downstream, in the opposite direction to that of the axial abutment 15 at the second axial end A of the rotor line. This axial stop 16 may be provided on the main body 11 of the last disc, as shown in Figure 2, or supported by a journal extending from the main body.

Referring to Figures 3a and 3b, the tie rod 10 is composed of a hollow tubular rod 17 supporting a head 18 at a second end 10A and a stop member 19 extending radially outwardly at a first end 10B. The tie rod 10 is placed axially inside the rotor line so that its first 10B and second 10A ends respectively correspond to the first B and second A ends of the rotor line.

The hollow rod 17 has a length L substantially corresponding to the distance between the abutments 15, 16 of the ends of the rotor line and whose value will be specified later, in relation to the clamping process. Likewise, the tie rod 10 is made of a material, for example a steel, the tensile strength of which makes it possible to withstand the forces required to clamp the discs 7 of the rotor line and whose mechanical properties will also be specified later.

Moreover, the hollow rod 17 preferably forms a smooth shaft in order to limit form overhearing shape accidents in order to withstand the traction forces. However, it may comprise stiffeners, bores or other elements depending on the needs related to the design of the turbomachine, such as, for example, dynamic stresses or cooling requirements.

The hollow rod 17 can support on its outer periphery a device 20 positioned so as to be at the inner ring of the second end A of the rotor line forming the stop 15, when the tie rod 10 is in place, so as to cooperate with said inner ring to ensure a seal. Here, this device 20 comprises two extra thicknesses forming a transverse groove on the outer circumference of the tie rod 10, in which it is possible to insert a seal, not shown, which bears on the inner radial surface of said inner ring forming the stop 15. Such a system may be useful for sealing a ventilation and cooling circuit of the blades of the rotor line stages. The stop element 19 has a transverse face turned downstream and having a substantially circular outer periphery and of diameter D3 significantly greater than the internal diameter D2 of the abutment 16 of the first end B of the rotor line, so as to block the pulling 10 in axial translation downstream relative to the rotor line, by axial support on this stop 16.

The head 18 advantageously comprises an excess thickness 21 from the second end 10A of the tie rod 10 and having, on the radially inner side, a transverse face 22 facing upstream. Here, this transverse face 22 forms the connection with the inner face of the hollow rod 17. The transverse face 22 forms a catch for a tool, not shown, that can be inserted radially inside the second end 10A of the pulling 10, in order to shoot downstream. Moreover, the extra thickness 21, preferably formed over the entire circumference of the tie rod 10, provides a reinforcement for the mechanical strength of the head 18 of the tie rod 10.

The head 18 is inscribed inside a circle of diameter D4 about the axis X, smaller than the diameter DI of the axial abutment 15 located at the second end A of the rotor line, so as to pass through.

The head 18 has on its radially outer periphery, at the extra thickness 21, 23 locking members for cooperating with a clamping latch 24, shown in Figures 2 and 5 to form a jabotée connection.

As can be seen in FIG. 4, the locking members are in the form of a circumferential succession of teeth 23 regularly spaced on the external surface of the head 18, which, in cross section, have the form of slots of width dl greater than their height h. Similarly, these teeth 23 have a length L1, along the X axis, greater than their height h.

Furthermore, the transverse face 25 facing upstream of the teeth 23, which is intended to form an axial abutment in a jaw-connected connection, is limited at these two circumferential ends by axial walls 26, 27 extending on the outer surface. of the excess thickness 21 in the upstream extension of the tooth 23. In this way, the circumferential width d2 of the transverse face 25 is slightly shorter than the circumferential width d1 of the tooth 23. Advantageously, the circumferential spacing between the teeth 23 has a width d3 equal to or slightly greater than the circumferential width d2 of the upstream transverse face, so as to allow the passage of an object having the same circumferential width as said upstream transverse face.

In the example under consideration, looking axially upstream and traversing the periphery in the direction of clockwise, each tooth 23 has a first wall 26 which extends beyond the first end of the face transverse 25 on a first length L2 and a second wall 27 which extends beyond the second end of the transverse face 25 on a second length L3. The first length L2 may have a value substantially equivalent to the length L1 of the tooth 23 and, advantageously, the first wall 26 extends substantially to the upstream end of the extra thickness 21. On the other hand, the second length L3 is significantly weaker. Its value can be discussed when describing the operation of the interconnected link and the clamping process. The example of latch 24 cooperating with the head 18, with reference to FIG. 5, is in the form of a circular ring 28 having on its internal radial surface a series of lugs 29 configured to cooperate with the teeth 23 of FIG. the head 18 to form the interconnected connection. The lock 24 is here oriented along the X axis of the tie rod 10 and the rotor line so that the ring 28 has a first transverse face 28A facing downstream and a second transverse face 28B facing upstream.

The lugs 29 also have a crenel-shaped transverse profile here, with a height of value substantially equal to the height h of the teeth 23 and a circumferential width of a value substantially equal to that of the upstream transverse faces 25 on said teeth 23. By elsewhere, the spacing d4 between two lugs 29 is substantially equal to the spacing between two upstream transverse faces on the head of the tie rod 10. In this way, first transverse faces 30 of the lugs 29, which are turned downstream , can be inserted between the walls 26, 27 of the teeth 23 of the tie rod 10 and cooperate in axial support with the upstream transverse faces of the teeth 23 to lock the latch 24 in translation downstream with respect to the tie rod 10.

The lugs 29 also have an axial length L4 of the same order of magnitude as the axial length L1 of the teeth 23 and can extend up to the upstream transverse face 28B of the ring 28.

Advantageously, the ring 28 of the lock 24 may comprise an excess thickness 31 at the lugs 29, forming a mechanical reinforcement similar to that 21 of the head 18 of the tie rod 10. Moreover, in correspondence with the height h of the lugs, the inner surface the ring 28 between the lugs 29 has a circular section having a diameter substantially adjusting to that of the outer face of the teeth 23 of the tie rod 10.

In the example presented, with reference to FIG. 2, the latch 24 is arranged in such a way that said transverse face 28B facing upstream bears against the abutment 15 of the rotor line in order to lock the latch 24 in translation towards upstream, when the lock 24 is installed on the tie rod 10.

In an associated manner, with reference to FIG. 5, the lugs 29 of the latch 24 are refined here on a portion starting from their upstream end and extend up to the upstream transverse face 28B to also bear against the stop 15. This form allows channeling the clamping force flow on the axial abutment 15 of the second end A of the rotor line. Moreover this portion of the lock can also pass around the sealing device 20 if the lock 24 is translated upstream on the tie rod 10.

We can now describe the operation of the interconnected link, then the clamping process.

Referring to Figure 6, the assembly of the latch 24 with the head 18 of the tie rod 10 is effected by a movement of the latch 24 relative to the tie rod 10 so that the lugs 29, and in particular their downstream face 30, follow a path represented by the dashed arrow: - The latch 24 is therefore first placed facing the head 18 so that the downstream faces 30 of the lugs 29 are in a position Pl facing the crenellations between the teeth 23 - A first axial translation of the latch 24 brings the downstream faces 30 of the lugs 29 in a position P2 upstream of the second wall 27 of the teeth 23. - in this example, a counterclockwise rotation of the latch 24 relative to the axis X in looking upstream, brings each pin 29 in circumferential abutment against the first wall 26 of each corresponding tooth 23 and their downstream face 30 in a position P3 in front of the upstream faces 25 of the teeth 23. - A second axial translation of the latch 24, from upstream v downstream, brings the transverse face 30 facing downstream of each lug 29 in a position P4, where it bears axially against the face 25 facing upstream of the corresponding tooth 23.

In the position P4 of the downstream faces 30 of the lugs 29, the latch 24 is thus maintained in axial abutment downstream by the cooperation of the transverse faces 30, 25 of the lugs 29 and the teeth 23. Moreover, the dimensions of the lugs 29 and teeth 23, in particular their axial lengths L1, L4, can be sized to withstand much greater tensile stresses than threads.

In addition, the walls 26, 27 block the pins 29 in rotation relative to the teeth 23 when their downstream faces 30 are supported in the position P4. The lugs 29 are therefore not likely to escape, for example because of vibration, during operation of the turbomachine, unlike a thread that requires additional tightening or a coating adapted to counteract the slippage that may occur during operation .

In the example shown, the first walls 26 have a length L2 for locking the lugs 29 of the latch 24 over their entire length in counterclockwise rotation relative to the teeth 23 of the tie rod 10. This is adapted to the case of a motor rotating in counter clockwise. It is of course possible to invert the circumferential position of the first and second walls, thus changing the mounting direction of the lock, especially for the case of a motor rotating in the clockwise direction.

Moreover, the differentiated lengths L2, L3 of the first 26 and second 27 lowermost walls on each tooth 23 make it possible to install the latch 24 on the head 18 in a simple manner by relying on the abutment against the first wall 26 during the rotation of the lock 24.

Finally, the length L3 of the second wall 27 must be sufficient to lock the latch 24 in rotation and prevent the accidental disconnection of the interconnected link but it may be relatively weak, not having to counter motor forces in this example. The lower it is, the less it imposes constraints on the realization of the lugs 29 to go to the position P2, allowing them to pass the second wall 27.

The dog-like connection thus described blocks the lock 24 downstream but not upstream. It remains to describe the entire tightening process to obtain the mounting of the tie rod 10 on the rotor line.

A first step of the process begins after the rotor line has been assembled, the disks 7a, 7b being contiguous with each other so that their complementary members 13 cooperate to form the coupling bonds by interlocking teeth, said "curvic coupling ". In this first step, with reference to part a) of FIG. 7, the tie rod 10 is introduced axially into the rotor line via the first end B of the latter, until the transverse face facing downstream of its abutment member 19 comes to bear on the abutment 16 of the first end B of the rotor line.

In this position the head 18 of the tie rod 10 is advantageously passed through the ring forming the abutment 15 of the second end A of the rotor line and the sealing device 20 is substantially facing said crown, so as to ensure its function as seal.

Furthermore, the tie rod 10 and the latch 24 are arranged in such a way that this position of the tie rod 10 corresponds, if the latch 24 was installed by the jaw-connected connection, to a position of the upstream transverse face 28B of the latch 24 which would be slightly offset upstream, a value ε, with respect to the downstream face of the abutment 15 on which it must bear.

In a second step, with reference to part b) of FIG. 7, the traction tooling 32 referred to above is hooked onto the attachment zone 22 of the tie rod 10. Then, using the pulling tool, pulling it to lengthen it with a length Δ which is slightly greater than the sum of the value ε of the offset observed at the end of the first step and the length L3 of the second wall 27 on the teeth 23. The elongation Δ Tie 10 is made using the elasticity properties of the material that forms it and must remain in values corresponding to an elastic deformation, before plasticization. For this reason, the length L3 of the second wall 27 will advantageously be chosen as the minimum that makes it possible to block the latch in rotation in a safe manner, and thus to reserve the maximum possible amplitude for the offset ε observed at the end of the first step. .

In a third step, with reference to part c) of FIG. 7, the latch 24 is installed on the head 18 to make the jaw-like connection in the manner that has been described above. The extension of the length L of the tie of the value Δ allows to leave the necessary clearance between the latch 24 and the abutment 15 of the rotor line to achieve this connection.

In a fourth step, with reference to part d) of FIG. 7, the traction on the tie rod 10 is released and the traction tooling 32 is removed. The tie rod 10 therefore retracts by a value equal to the difference between the value Δ and the value ε. The latch 24 is thus locked between the head 18 of the tie rod 10, by the clutch link, and the stop 15 of the second end A of the rotor line. At the end of this fourth step, the tie 10 is in a state where its length is greater than the value ε at its length L at rest during the first step. It therefore exerts on the rotor line, via its stop element 19 at one end 10B and the latch 24 at the other end 10A, a compression of the rotor line between its two ends A, B to maintain the connection 13 between the disks 7a, 7b.

The value of the tightening exerted by the tie rod 10 on the rotor line 7 is determined by calculation and is adapted by the length L of the tie rod 10. In order to obtain a stronger tightening value, the length L of the tie rod 10 must be shortened so to increase the shift ε and vice versa to decrease it.

The value limit of the tightening is determined by the maximum elongation before plasticization. For example, for a Young's modulus material E = 200,000 MPa, an elastic limit of R0 = 850 MPa and a nominal length L = 1m of the tie rod 10, it will be possible to lengthen it, during the third step , of a value Δ = (R0 / E) x L, equal to 4.25 mm.

The device and method have been presented here for a rotor line on a high pressure turbine but it is obvious to those skilled in the art that the invention can be applied to other rotor lines on a turbomachine. In particular, it is conceivable to apply the "curvic coupling" technique and the clamping method which has just been described to the rotor assembly of the high pressure body, comprising the compressor 2 and the turbine 4.

Furthermore, the device has been presented by placing the lugs 29 in the latch 24 and the complementary teeth 23 on the head 18 of the tie rod 10 but an inverted configuration can be easily envisaged. On the other hand, the method has been presented by increasing the length of the rod 17 of the tie rod 10, when its first end 10B abuts the first end B of the rotor line and its second end 10A is free, pulling on this second end with a tool 32. Other ways of extending the rod 17 of the tie rod can be envisaged. For example, the tie rod to be assembled to the rotor line under given temperature conditions, the length of the rod 17 can be increased by heating the rod 17 differentially with respect to the rotor line. By adjusting the temperature difference for a given coefficient of expansion of the material of the rod, it is then possible temporarily to obtain an increase in length Δ which makes it possible to install the latch 24 with the link that is clutched onto the head 18 of the tie rod. In a next step, when the rod 17 cools, it retracts to its original length L and thus applies a clamping force comparable to that obtained previously.

Claims (4)

claims 1. A method of clamping a turbomachine rotor line (7) composed of at least two elements (7a, 7b) contiguous along an axis (X), in particular of rotation of the rotor, comprising: an insertion step along said axis (X) of an elongate tie rod (10) substantially in the center of said elements for bringing a first longitudinal end (10B) of the tie rod (10) into axial abutment against a first axial end (B) of the rotor line (7), the tie rod (10) having a given length (L) in a first state such as a second longitudinal end (10A) of the tie rod (10) is substantially at a second axial end (A) of the rotor line (7), opposite said first axial end (B), and - submitting the tie rod (10) to stresses to bring said tie rod into a second state in which its length (L) is increased by a value ( Δ), characterized in that it also comprises steps of: releasing a latch (24) on the second longitudinal end (10A) of the tie rod (10) by a dog-type connection (23-29), when the tie rod (10) is under stress, in the second state, and in abutment against the first axial end (B) of the rotor line (7), and - release of the constraints of the tie rod (10), so as to let it return to a third state, in which its length takes a value (L + ε ) intermediate between those of the first (L) and the second state (L + Δ) and stop means (28B) of said latch (24) bear on a portion (15) of the second axial end (A) of the rotor line ( 7), so as to tighten the rotor line (7) between its two longitudinal ends (10B-A) along the axis (X). 2. Method according to the preceding claim, wherein the passage of the tie rod (10) of the first state to the second state is by subjecting it to a traction directed along the axis (X) at its second longitudinal end (10A) . 3. Device for implementing the method according to one of the preceding claims, comprising an elongated tie rod (10) and a latch (24), the tie rod (10) having first means (19) installed on a first longitudinal end (10B) of the tie rod (10) and forming a longitudinal stop facing towards a second longitudinal end (10A), opposite to the first longitudinal end, characterized in that the second longitudinal end (10A) of the tie rod (10) comprises a first circumferential succession of teeth (23) arranged to cooperate with a second circumferential succession of teeth (29) arranged on the latch (24), to form a jaw-like connection blocking the lock (24) longitudinally in the direction from the first longitudinal end (10B) towards the second (10A), and in that the lock (24) comprises second means (28B) arranged to form, when the link of type e clutch is produced, a second longitudinal abutment facing the first longitudinal end (10A) of the tie rod (10). 4. Device according to the preceding claim, wherein at least one of the teeth (23) of one of the circumferential succession of teeth comprises first circumferential abutment means (26) disposed at a first circumferential end of a face ( 25) serving as a support for the dog type connection and extending longitudinally from said face (25). 5. Device according to the preceding claim, wherein said at least one tooth (23) comprises second circumferential abutment means (27) disposed at the second circumferential end of said face (25) serving as a support for the dog-type connection. and extending longitudinally from said face (25) a distance (L3) less than that (L2) of said first circumferential abutment means (26). 6. Device according to one of claims 3 to 5, wherein the tie rod (10) has a hollow tubular shape. 7. Device according to the preceding claim, wherein the tie rod (10) has an extra thickness (21) substantially in line with the circumferential succession of teeth (23) participating in the dog type connection. 8. Device according to the preceding claim, wherein the extra thickness (21) comprises a portion arranged to cooperate with a tool (32) of traction or tension. 9. A turbomachine assembly comprising a rotor line (7) formed of at least two elements (7a, 7b) contiguous along an axis (X) and a device according to one of claims 3 to 8, said assembly being arranged such that so that: - said elements of the rotor line are arranged to be traversed along the axis (X) by the tie rod (10), - a first axial stop (16) is arranged on a first axial end (B) of the line rotor (7) so as to cooperate with the first longitudinal stop means (19) of the tie rod (10), - a second axial stop (15) is arranged on the second axial end (A) of the rotor line (7). in order to cooperate with the second longitudinal abutment means (28B) arranged on the latch (24), and - said tie rod (10) passing through the rotor line (7) along the axis (X), the first means (19) of longitudinal stop of the tie rod (10) bearing against the abutment (16) of the first axial end (B) of the a rotor line (7) and the latch (24) being installed on the tie rod (10) by the connection of the dog type, being in axial bearing in one direction against the tie rod (10) and in the opposite direction against the axial stop (15) of the second axial end (A) of the rotor line (7). 10. Turbomachine comprising an assembly according to the preceding claim.