WO2020249686A1

WO2020249686A1 - Dynamic balancing device for rotor

Info

Publication number: WO2020249686A1
Application number: PCT/EP2020/066224
Authority: WO
Inventors: Etienne Romain Pascal Grenier
Original assignee: Safran Aircraft Engines
Priority date: 2019-06-11
Filing date: 2020-06-11
Publication date: 2020-12-17
Also published as: FR3097268B1; FR3097268A1

Abstract

The present invention concerns a dynamic balancing device (1) for a rotor, the rotor being able to rotate relative to a housing around a longitudinal axis (X-X), the device (1) comprising: - a support shaft (100) suitable for being fixedly mounted on the rotor, extending along the longitudinal axis (X-X), - a first flyweight (11) mounted so as to be able to rotate on the support shaft (100) around the longitudinal axis (X-X), and - a second flyweight (12) mounted so as to be able to rotate on the support shaft (100) around the longitudinal axis (X-X).

Description

DYNAMIC BALANCING DEVICE FOR ROTOR

FIELD OF THE INVENTION

The present invention relates to the balancing of a rotor.

More specifically, the present invention relates to a device and a dynamic balancing method for a rotor, for example a turbomachine rotor.

STATE OF THE ART

A rotor movable in rotation with respect to a casing about a longitudinal axis is liable to be unbalanced.

An unbalance corresponds to a localized imbalance of the rotor. An unbalance can, for example, arise from manufacturing defects of the rotor, develop following wear of the rotor, or even appear thanks to unsteady aerodynamic phenomena when all or part of the rotor is coupled to a circulation of fluid during its rotation.

An unbalance generally causes vibrations within the rotor, when the latter rotates around the longitudinal axis. Such vibrations are detrimental to the correct functioning of the rotor.

Balancing a rotor is therefore an essential step in its design and operation.

Several solutions for balancing a rotor exhibiting unbalance have already been proposed.

A so-called "static" solution involves disassembling the rotor in order to install a set of balancing weights at given rotor positions. Such static balancing therefore requires both the immobilization of the rotor as such, but also structures to which said rotor is linked. Furthermore, determining the number and positions of the weights is a tedious, sophisticated and expensive undertaking.

So-called “dynamic” solutions have therefore been proposed. Dynamic rotor balancing devices are, in fact, known from the state of the art, and make it possible to automate the balancing of the rotor. One of these devices has, for example, been described in document FR 3 004 418, in the name of the Applicant. In this device, two weights are movable along a guide slide surrounding the longitudinal axis of a turbomachine rotor, as a function of an estimate of the unbalance of said rotor.

However, such devices are not entirely satisfactory. In particular, the two weights cannot take the same angular position around the longitudinal axis, since they necessarily come into abutment against one another. Consequently, the fineness of correction of an unbalance is not optimal.

There is therefore a need to at least overcome the drawbacks of the state of the art.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide dynamic balancing of a rotor in a reliable, simple and inexpensive manner.

To this end, there is proposed, according to a first aspect of the invention, a dynamic balancing device for a rotor, said rotor being movable in rotation with respect to a casing about a longitudinal axis, the device comprising:

- a support axis suitable for being mounted fixed on the rotor, extending along the longitudinal axis,

- a first flyweight mounted to rotate on the support axis around the longitudinal axis, and

- a second flyweight mounted so as to be able to rotate on the support axis about the longitudinal axis.

In such a dynamic balancing device, it is no longer necessary to modify the radial position or the mass of a balancing weight to determine and / or correct a rotor unbalance. Indeed, it suffices to exploit the phase shift between the two weights, which also provides a finer correction. In addition, it is less costly in terms of energy to rotate the weights than to move them radially, since it is no longer necessary to combat the centrifugal forces generated by the rotor when it is rotated. This is all the more advantageous in that the rotors to be balanced are of small dimensions, such as, for example, experimental rotor models.

Advantageously, but optionally, the device according to the invention can include at least one of the characteristics below, taken alone or in combination:

- each of the first weight and the second weight is capable of being rotated around the longitudinal axis without interfering with the other of the first weight and the second weight,

- the first flyweight is offset from the second flyweight along the longitudinal axis,

- it further comprises a support, the support axis having:

o a first end portion projecting from a first surface of the support, o a second end portion projecting from a second surface of the support, opposite the first surface,

o the first weight being mounted so as to be able to rotate on the first end part, and

o the second weight being mounted so as to be able to rotate on the second end part,

- it also includes:

o a first motor configured to drive the first flyweight in rotation, and o a second motor configured to drive the second flyweight in rotation, each of the first motor and the second motor being configured to be fixedly mounted on the rotor,

- at least one of the first motor and the second motor is an electric motor, and

- the first weight has a shape complementary to the second weight so that, when the first weight and the second weight are positioned with respect to each other with a predefined angular offset, around the longitudinal axis, the device exerts no unbalance on the rotor.

According to a second aspect of the invention, there is provided an assembly for a turbomachine comprising:

- a housing,

- a rotor movable in rotation with respect to the housing about a longitudinal axis, and

- a dynamic balancing device for a rotor as described above.

According to a third aspect of the invention, there is provided a turbomachine comprising an assembly as described above.

According to a fourth aspect of the invention, there is provided a method of dynamic balancing of a rotor, said rotor:

- being movable in rotation with respect to a housing around a longitudinal axis, and

- having an unbalance having a radial direction and an intensity,

the method comprising steps of:

- Rotation of a first weight relative to a second weight about a support axis fixedly mounted on the rotor, and extending along the longitudinal axis, so that the first weight and the second weight occupy a common angular sector, and

- simultaneous rotation of the first weight and the second weight in phase with the first weight around the support axis so as to:

o keep the common angular sector constant, and o moving said common angular sector around the support axis until the common angular sector is aligned with the radial direction of the unbalance.

Advantageously, but optionally, the method according to the invention can further comprise a step of simultaneously rotating the first flyweight and the second flyweight, the first flyweight being moved in phase opposition with the second flyweight about the axis support so as to:

- increase the common angular sector, and

- until compensating for the intensity of the unbalance.

DESCRIPTION OF FIGURES

Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and not limiting, and which should be read with reference to the accompanying drawings in which:

Figure 1 is a schematic sectional view of a turbomachine.

Figure 2 is a schematic sectional view of an assembly comprising an exemplary embodiment of a dynamic balancing device according to the invention.

Figure 3 schematically illustrates part of an exemplary implementation of a dynamic balancing method according to the invention.

FIG. 4 schematically illustrates another part of an example of implementation of a dynamic balancing method according to the invention.

FIG. 5 is a flowchart illustrating an example of the implementation of a dynamic balancing method according to the invention.

In all of the figures, similar elements bear identical references.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the figures, a device 1 and a dynamic balancing method E for a rotor, typically a turbomachine rotor 2, will now be described.

With reference to FIG. 1, a turbomachine 2 comprises at least one casing 20, for example a set of casings forming a fairing (ie stator assembly) 20, a fan 21, a low pressure compressor 22, a high pressure compressor 23, a chamber combustion chamber 24, a high pressure turbine 25 and a low pressure turbine 26. Each of the blower 21, of the low pressure compressor 22, of the high pressure compressor 23, of the high pressure turbine 25, and of the low pressure turbine 26, comprises a rotor movable in rotation with respect to the casing 20 about a longitudinal axis XX. In addition, the fan 21 comprises a plurality of blades 210 fixed by their foot to a hub 212 on which is fixed an air inlet cone 214 centered on the longitudinal axis XX.

In the embodiment illustrated in FIG. 1, the fan 21 and the low pressure compressor 22 are integral in rotation, and are capable of being set in rotation by a low pressure shaft 27 which is itself capable of being put into operation. rotation by the low pressure turbine 26. The assembly formed by the fan 21, the low pressure compressor 22, the low pressure shaft 27 and the low pressure turbine 26, forms the low pressure body. The high pressure compressor 23 is, for its part, capable of being rotated by a high pressure shaft 28, which is itself capable of being rotated by the high pressure turbine 25. The assembly formed by the high pressure compressor 23, the high pressure shaft 28 and the high pressure turbine 25, form the high pressure body. The positioning of each of the low pressure shaft 27 and the high pressure shaft 28 is provided by a set of bearings (not shown).

In operation, the blower 21 draws in an air flow which separates between a secondary flow, circulating around the assembly 20 of casings, and a primary flow, successively compressed within the low pressure compressor 22 and the high pressure compressor 23 , ignited within the combustion chamber 24, then successively expanded within the high pressure turbine 25 and the low pressure turbine 26.

Upstream and downstream are here defined relative to the direction of normal air flow through the turbomachine 2 in operation. Likewise, an axial direction corresponds to the direction of the longitudinal axis XX, a radial direction is a direction which is perpendicular to this longitudinal axis XX and which passes through said longitudinal axis XX, and a circumferential or tangential direction corresponds to the direction of a flat, closed curved line, all points of which are equidistant from the longitudinal axis XX. Finally, and unless otherwise specified, the terms "internal (or internal)" and "external (or external)", respectively, are used with reference to a radial direction such that the part or the internal face (ie radially internal) d an element is closer to the longitudinal axis XX than the part or the external face (ie radially external) of the same element.

A rotor, such as a turbomachine rotor 2, is liable to be unbalanced. An unbalance corresponds to a localized imbalance of the rotor and generally causes vibrations within the rotor, during the rotation of the latter around the longitudinal axis XX which is its axis of rotation. An unbalance is characterized in particular by a radial direction, a distance from the axis of rotation XX of the rotor, and an intensity. It can also be measured according to different methods. For example, it is possible to measure the unbalance of the blower 21 by placing one or more vibration sensors, such as accelerometers, at one or more bearings of the low pressure shaft 27, the unbalance then being deduced from overall models using the measurements obtained from the sensors of vibration. In order to balance a rotor and eliminate an unbalance, it is advantageous to artificially create a counter-unbalance, of the same intensity, of the same radial direction, but opposite to the unbalance with respect to the axis of rotation XX of the rotor.

Thus, balancing the rotor requires knowing precisely the unbalance in order to be able to correct it. This is particularly advantageous during the design of the turbomachine 2, for example during work carried out on models of said turbomachine 2.

Referring to Figure 2, a dynamic balancing device 1 of a rotor 21, 22, 27, 26 movable in rotation relative to a set 20 of housings around a longitudinal axis, such as a turbomachine rotor 2, for example a low-pressure body model 21, 22, 27, 26 of a turbomachine 2, comprises:

- a support axis 100 suitable for being fixedly mounted on the rotor, extending along the longitudinal axis X-X,

- a first flyweight 11 mounted to rotate on the support axis 100 around the longitudinal axis X-X, and

- a second flyweight 12 rotatably mounted on the support axis 100 around the longitudinal axis X-X.

The support axis 100 is thus integral in rotation with the rotor about the longitudinal axis X-X. In addition, unlike devices of the state of the art where weights were arranged at a distance from the longitudinal axis XX, the fact that the support axis 100 extends along the longitudinal axis XX makes it possible to s' free from centrifugal forces exerted by the weights 11, 12 on the shaft 27 driving the rotor 21, 22, 27, 26 in rotation, and also extending along the longitudinal axis XX. In any event, by varying the angular position of the two weights 1 1, 12 around the longitudinal axis XX, it is possible to create a counter-unbalance varying between 0 and 2 times the individual unbalance of each weight 1 1 , 12.

In one embodiment, for example illustrated in FIG. 2, the dynamic balancing device 1 comprises a support 10 suitable for being mounted fixedly on the rotor, so as to be integral in rotation with the rotor. As shown in Figure 2, the support axis 100 has:

- a first end part 1001 projecting from a first surface of the support 10,

- a second end part 1002 projecting from a second surface of the support 10, opposite the first surface.

In this embodiment, the first flyweight 11 is mounted to be movable in rotation on the first end part 1001, and the second weight 12 is mounted to be movable in rotation on the second end part 1002. Each of the first flyweight 11 and the second flyweight 12 is advantageously capable of being rotated around the longitudinal axis XX without interfering with the other of the first flyweight 11 and the second flyweight 12. This allows the dynamic balancing device 1 to provide a finer unbalance correction, because the two weights 11, 12 can occupy the same angular position around the longitudinal axis XX, without coming into abutment against one another. In other words, the counterbalance created can take any angular position around the longitudinal axis XX. In the embodiment illustrated in FIG. 2, the first weight 11 is offset axially with respect to the second weight 12, that is to say it is offset with respect to the second weight 12 along the axis longitudinal XX. This is not, however, limiting, the first weight 11 and the second weight 12 being able to be arranged in the same position along the longitudinal axis XX. In this case, one of the first flyweight 11 and the second flyweight 12 is, for example, hollowed out with a slot having a shape complementary to the other of the first flyweight 11 and the second flyweight 12 so that the latter can be driven in rotation about the longitudinal axis XX without interfering with that of the first weight 11 and of the second weight 12 which is hollowed out. When the first weight 11 and the second weight 12 occupy the same position along the longitudinal axis XX, their axial size is reduced.

In any event, as can be seen in Figures 3 and 4, each of the first flyweight 11 and the second flyweight 12 advantageously has the shape of a half-disc, the first flyweight 11 preferably being identical to the second flyweight 12 In this way, the space occupied by the dynamic balancing device 1 is optimized. In one embodiment, the first flyweight 11 has a shape complementary to the second flyweight 12 so that, when the first flyweight 11 and the second flyweight 12 are positioned relative to each other with a predefined angular offset around of the longitudinal axis XX, typically 180 °, the dynamic balancing device 1 exerts no unbalance on the rotor.

The dynamic balancing device 1 may, in one embodiment, comprise more than two weights 11, 12. In this case, the other weights may or may not be offset axially relative to the first weight 11 and to the second weight 12, and / or be, or not, offset axially with respect to each other. The additional weights make it possible in particular to correct imbalances in the form of moments of inertia with respect to the longitudinal axis X-X.

In one embodiment, at least one of the first flyweight 11 and the second flyweight 12 comprises a dense material, preferably with a density of between 15 and 20 tonnes per cubic meter. In a preferred variant, the two weights 1 1, 12 include a material, for example Triamet® G19, which has a density of 18 tonnes per cubic meter. Each of the weights 1 1, 12 then advantageously has an unbalance of between 75 and 150 cm. g, preferably equal to 100 cm. g, which is in particular sufficient for balancing unbalances of experimental rotors in the form of models.

Still with reference to Figure 2, in one embodiment, the dynamic balancing device 1 comprises:

- a first motor 13 configured to drive the first weight 11 in rotation, and

a second motor 14 configured to drive the second flyweight 12 in rotation. Each of the first motor 13 and of the second motor 14 is configured to be fixedly mounted on the rotor, for example by being suitable for being fixedly mounted on a support 15, 16 corresponding, the supports 15, 16 of the motors 13, 14 can then be fixed to the support 10 of the weights, for example by means of bolted screws 18 passing through each of these three supports 10, 15, 16.

Advantageously, at least one of the first motor 13 and the second motor 14 is an electric motor. It is indeed an engine that can easily be made compact, which can be particularly interesting when the dynamic balancing device 1 is used in a model, of reduced dimensions.

Alternatively, at least one of the first motor 13 and the second motor 14 is configured to drive the weights 11, 12 at speeds between 10,000 and 15,000 revolutions per minute, preferably 12,000 revolutions per minute.

In a preferred variant, the drive axis 130, 140 of each of the first motor

13 and the second motor 14 extends along the support axis 10. This makes it possible to relieve the bearings (not shown) of the motors 13, 14 so that the support axis 10 takes up the forces exerted by the weights 11, 12 and not the drive shafts 130, 140 of the motors 13, 14. In other words, this makes it possible to limit the centrifugation of the motors 13, 14. In any event, the drive gears (not shown) 13 engines,

14 are flexible.

Alternatively, at least one of the first motor 13 and of the second motor 14 drives the corresponding flyweight 11, 12 via a reduction mechanism (not shown). This makes it possible to generate a significant torque on the weight 11, 12. In addition, this makes it possible to make the dynamic balancing device 1 irreversible. Indeed, the rotating forces seen by the weights 11, 12 are thus not applied to the motors 13, 14, which protects the latter. The use of a reduction mechanism is moreover all the more advantageous as the driving speed of the motors 13, 14 is high. Finally, the reduction mechanism can serve as a safety mechanism in the event of failure of the motors 13, 14. In this case, the weights 1 1, 12 could indeed generate a greater unbalance. at the initial unbalance of the rotor. The presence of the reduction mechanism makes it possible to keep the weights 11, 12 in their position at the time of failure, the time to perform maintenance.

In one embodiment, the dynamic balancing device 1 is controllable remotely. To do this, it typically includes a computer (not shown). In addition, in order to ensure the control and the supply of electric power to the motors 13, 14 in a frame, it comprises a telemetry (not shown) which allows signals to be transmitted between a rotating frame and a fixed frame, and comprises for example two rotary transformers, one for the electric power, and the other for the relay of weak signals. In other embodiments, the electrical power supply is provided by accumulators (not shown) on board the dynamic balancing device 1, the commands being relayed by means of intangible media such as Wifi or Bluetooth.

The dynamic balancing device 1 can typically be controlled as follows. A balancing (or unbalancing) order is sent to the dynamic balancing device 1, once the latter is mounted on a rotor to be balanced (or unbalanced). This order can, for example, consist of a counter-unbalance (or unbalance) objective, that is to say to reach a specific counter-unbalance (or unbalance) value for the rotor.

The computer receives the order and compares it to the dynamic situation of the rotor, typically using the data provided by the vibration sensors arranged at the bearings of the rotor. It then controls the operation of the motors 13, 14 which rotate the weights 1 1, 12 around the longitudinal axis, and return the positions reached to the computer. By slaving, the computer then refines the position of the weights 1 1, 12 in order to achieve the fixed counter-unbalance.

More specifically, with reference to Figures 3 to 5, a dynamic balancing process E of a rotor comprises the following steps. In these figures the unbalance of the rotor is symbolized by a disc connected by a rod to the longitudinal axis X-X. The radius of the disc corresponds to the intensity of the unbalance, the length of the rod corresponds to the distance of the unbalance from the longitudinal axis X-X, and the direction of the rod corresponds to the radial direction of the unbalance. Advantageously, the dynamic balancing process E described is implemented during the operation of the rotor, that is to say when the rotor is set in rotation with respect to the housing 20 around the longitudinal axis X-X.

In a first step, the radial direction of the unbalance is sought. In other words, the angular position of the unbalance seeks to be determined.

To do this, as visible in FIG. 3, the first weight 11 is first of all rotated E1 relative to the second weight 12 around the support axis 10 so that the first weight 11 and the second flyweight 12 occupy a common angular sector A. In other words, the flyweights 1 1, 12 are rotated one by one relative to the other so as to be positioned at 180 ° from each other (ie symmetrically opposite to each other with respect to the longitudinal axis), within an angular opening O near. Then, still with reference to FIG. 3, the first weight 11 and the second weight 12 are rotated E2 simultaneously in phase with the first weight 11 around the support axis 10 so as to:

- keep the common angular sector A constant, and

- moving said common angular sector A around the support axis 10 until the common angular sector A is aligned with the radial direction of the unbalance.

In fact, when the angular opening O between the two weights 11, 12 aligns with the radial direction of the unbalance, the dynamic situation of the rotor improves. Indeed, the counter-unbalance formed by the common angular sector A of the two weights 11, 12 is in the same radial direction as the unbalance of the rotor.

In a second step, the intensity of the unbalance is sought and counterbalanced. To do this, as visible in Figure 4, the first flyweight 11 and the second flyweight 12 are placed in simultaneous rotation E3, the first flyweight 11 being moved in phase opposition with the second flyweight 12 around the support axis 10 in order to :

- increase the common angular sector A, and

- until compensating for the intensity of the unbalance.

More precisely, the two weights 1 1, 12 are rotated with equal speeds but opposite directions of rotation until the dynamic situation of the rotor becomes low, that is to say that the assembly formed by the rotor and the dynamic balancing device 1 have a total residual unbalance (ie the sum of the initial unbalance of the rotor and the counter-unbalance formed by the two weights 11, 12) which is minimal. The common angular sector A is then centered on the radial direction of the unbalance, and opposite the unbalance with respect to the longitudinal axis X-X.

In the case where it is a question of intentionally unbalancing the rotor, that is to say where an unbalance greater than the initial unbalance of the rotor is sought, the weights 1 1, 12 are rotated simultaneously around the axis of support 10, the first weight 11 being displaced in phase opposition with the second weight 12, so as to increase the intensity of the initial unbalance, that is to say until the intensity of the unbalance is worsened. In other words, the common angular sector A is then centered on the radial direction of the unbalance, but this time on the same side as the unbalance with respect to the longitudinal axis X-X.

In the embodiment illustrated in FIG. 2, the dynamic balancing device 1 is housed within the cone 214 of the fan 21 of the turbomachine 2. This is not, however, limiting, since such a device d dynamic balancing 1 can be arranged at any position within the low pressure body 21, 22, 27, 26. By virtue of the device 1 and the dynamic balancing method E described, it is possible to adjust the balancing of a rotor without stopping the machine, or removing parts to gain access to the balancing zones and implement the adjustments. Even, it is possible to intentionally unbalance the rotor, for example during the design work of said rotor, in order to study its behavior, typically on a model. These elements are in particular advantageous for autonomously and automatically correcting the unbalance of a rotor, whether during maintenance, during manufacture, for example in series production, or during test phases on said rotor. In any event, by virtue of the device 1 and the dynamic balancing method E described, it is possible to directly determine the unbalance of a rotor. For example, this determination can be implemented by means of a dynamic model linking the information acquired by the vibration sensors and that relating to the relative position of weights around the longitudinal axis. This is in particular simpler and more efficient than the methods of determining unbalance known from the state of the art, where the unbalance is determined by reading the number and the radial position of weights making it possible to await a fixed vibratory situation.

In everything that has been described above, the turbomachine 2 is of the double-body, double-flow, direct-drive turbojet type. This is not, however, limiting, given that the device 1 and the dynamic balancing method E described can also be used for any type of turbomachine 2, such as a turboprop, a turbojet having a gearbox architecture, or a turbomachine of the triple-body, double-flow type, whether it be moreover models or full-size turbomachines.

Claims

1. Dynamic balancing device (1) for a rotor, said rotor being movable in rotation with respect to a housing about a longitudinal axis (X-X), the device (1) comprising:

- a support axis (100) suitable for being fixedly mounted on the rotor, extending along the longitudinal axis (X-X),

- a first flyweight (11) mounted to be able to rotate on the support axis (100) around the longitudinal axis (X-X),

- a second flyweight (12) mounted to rotate on the support axis (100) around the longitudinal axis (X-X),

- a first motor (13) configured to drive the first weight (11) in rotation, and

- a second motor (14) configured to drive the second flyweight (12) in rotation, each of the first motor (13) and of the second motor (14) being configured to be fixedly mounted on the rotor.

2. Device according to claim 1, wherein each of the first flyweight (1 1) and the second flyweight (12) is capable of being rotated around the longitudinal axis (XX) without interfering with the other. of the first flyweight (11) and the second flyweight (12).

3. Device according to one of claims 1 and 2, wherein the first weight (1 1) is offset from the second weight (12) along the longitudinal axis (X-X).

4. Device according to claim 3, further comprising a support (10), the support axis (100) having:

- a first end part (1001) projecting from a first surface of the support (10),

- a second end part (1002) projecting from a second surface of the support (10), opposite the first surface,

- the first weight (11) being mounted so as to be able to rotate on the first end part (1001), and

- the second flyweight (12) being mounted so as to be able to rotate on the second end part (1002).

5. Device according to one of claims 1 to 4, wherein at least one of the first motor (13) and the second motor (14) is an electric motor.

6. Device according to one of claims 1 to 5, wherein the first weight (11) has a shape complementary to the second weight (12) so that, when the first weight (11) and the second weight (12) are positioned relative to each other with a predefined angular offset, around the longitudinal axis (XX), the device (1) exerts no unbalance on the rotor.

7. Turbomachine assembly (2) comprising:

- a housing (10),

- a rotor (21, 22, 27, 26) movable in rotation relative to the housing (10) about a longitudinal axis (X-X), and

- a dynamic balancing device (1) for a rotor according to one of claims 1 to 6.

8. Turbomachine (2) comprising an assembly according to claim 7.

9. Method of dynamic balancing (E) of a rotor, said rotor:

- being movable in rotation relative to a housing around a longitudinal axis (X-X), and

- having an unbalance having a radial direction and an intensity,

the method (E) comprising steps of:

- rotation (E1) of a first flyweight (1 1) relative to a second flyweight (12) about a support axis (100) mounted fixed on the rotor, and extending along the longitudinal axis (XX), so that the first flyweight (1 1) and the second flyweight (12) occupy a common angular sector (A), and

- simultaneous rotation (E2) of the first flyweight (1 1) and the second flyweight (12) in phase with the first flyweight (1 1) around the support axis (100) so as to: o maintain constant the common angular sector (A), and

o moving said common angular sector (A) around the support axis (100) until the common angular sector (A) is aligned with the radial direction of the unbalance.

10. The method of claim 9, further comprising a step of simultaneous rotation (E3) of the first weight (1 1) and the second weight (12), the first weight (11) being displaced in phase opposition. with the second weight (12) around the support axis (100) so as to:

- increase the common angular sector (A), and

- until compensating for the intensity of the unbalance.