FR3097268A1 - Dynamic balancing device for rotor - Google Patents

Abstract

The present invention relates to a dynamic balancing device (1) for a rotor, said rotor being movable in rotation relative to a housing about a longitudinal axis (XX), the device (1) comprising: - a support axis ( 100) suitable for being mounted fixedly on the rotor, extending along the longitudinal axis (XX), - a first weight (11) mounted so as to be able to rotate on the support axis (100) around the longitudinal axis (XX), and- a second flyweight (12) mounted so as to be able to rotate on the support axis (100) around the longitudinal axis (XX). Figure for the abstract: Fig. 2

Description

Dynamic balancing device for rotor

The present invention relates to the balancing of a rotor.

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

A rotor that rotates relative to a casing around a longitudinal axis is likely to be unbalanced.

An imbalance corresponds to a localized imbalance of the rotor. An imbalance can, for example, arise from manufacturing defects in the rotor, develop following wear of the rotor, or even appear in favor of 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, during the rotation of the latter around the longitudinal axis. Such vibrations are harmful to the proper functioning of the rotor.

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

Several solutions for balancing a rotor with an imbalance have already been proposed.

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

So-called “dynamic” solutions have therefore been proposed. Dynamic balance devices for rotors 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 flyweights are movable along a guide slideway surrounding the longitudinal axis of a turbomachine rotor, depending on 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 each other. Consequently, the fineness of imbalance correction is not optimal.

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

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

For this purpose, according to a first aspect of the invention, a dynamic balancing device for a rotor is proposed, said rotor being rotatable relative to a casing around a longitudinal axis, the device comprising:
- a support axis adapted to be mounted fixed on the rotor, extending along the longitudinal axis,
- a first flyweight mounted mobile in rotation on the support axis around the longitudinal axis, and
- A second flyweight mounted rotatably on the support axis around 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 imbalance. Indeed, it is enough 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 fight against the centrifugal forces generated by the rotor when it is rotated. This is moreover all the more advantageous when the rotors to be balanced are of reduced dimensions, such as, for example, the models of experimental rotors.

Advantageously, but optionally, the device according to the invention may comprise at least one of the characteristics below, taken alone or in combination:
- each of the first flyweight and the second flyweight is capable of being rotated around the longitudinal axis without interfering with the other of the first flyweight and the second flyweight,
- the first flyweight is offset from the second flyweight along the longitudinal axis,
- it further comprises a support, the support pin having:
○ a first end part protruding from a first surface of the support,
○ a second end part protruding from a second surface of the support, opposite the first surface,
○ the first flyweight being rotatably mounted on the first end part, and
○ the second flyweight being rotatably mounted on the second end part,
- it also includes:
○ a first motor configured to drive the first flyweight in rotation, and
○ a second motor configured to drive the second flyweight in rotation,
each of the first motor and of 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 flyweight has a complementary shape to the second flyweight so that, when the first flyweight and the second flyweight are positioned relative to each other with a predefined angular offset, around the longitudinal axis, the device does not exert any unbalance on the rotor.

According to a second aspect of the invention, there is proposed an assembly for a turbomachine comprising:
- a casing,
- a rotatable rotor relative to the housing around a longitudinal axis, and
- a dynamic balancing device for the rotor as previously described.

According to a third aspect of the invention, a turbomachine is proposed comprising an assembly as previously described.

According to a fourth aspect of the invention, there is proposed a method for dynamically balancing a rotor, said rotor:
- being rotatable relative to a casing around a longitudinal axis, and
- presenting an unbalance having a radial direction and an intensity,
the method comprising steps of:
- rotation of a first flyweight relative to a second flyweight around a support axis mounted fixed on the rotor, and extending along the longitudinal axis, so that the first flyweight and the second flyweight occupy a common angular sector, and
- simultaneous rotation of the first flyweight and the second flyweight in phase with the first flyweight around the support axis so as to:
○ keep the common angular sector constant, and
○ 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 also 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 around the axis of support so as to:
- increase the common angular sector, and
- until the intensity of the unbalance is compensated.

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, and which must be read in conjunction with the appended 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 embodiment of a dynamic balancing device according to the invention.

FIG. 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 exemplary implementation of a dynamic balancing method according to the invention.

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

In all the figures, similar elements bear identical references.

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

Referring to Figure 1, a turbomachine 2 comprises at least one casing 20, for example a set of casings forming a shroud (i.e. stator set) 20, a fan 21, a low pressure compressor 22, a high pressure compressor 23, a chamber combustion engine 24, a high pressure turbine 25 and a low pressure turbine 26.

Each of the fan 21, the low pressure compressor 22, the high pressure compressor 23, the high pressure turbine 25, and the low pressure turbine 26, comprises a rotor movable in rotation relative to the casing 20 around a longitudinal axis X-X. 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 X-X.

In the embodiment illustrated in Figure 1, the fan 21 and the low pressure compressor 22 are integral in rotation, and are capable of being rotated by a low pressure shaft 27 which is itself capable of being put into 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, high pressure shaft 28 and high pressure turbine 25 form the high pressure body. The positioning of each of the low pressure shaft 27 and of the high pressure shaft 28 is ensured by a set of bearings (not shown).

In operation, the fan 21 draws in a flow of air 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. Similarly, an axial direction corresponds to the direction of the longitudinal axis X-X, a radial direction is a direction which is perpendicular to this longitudinal axis X-X and which passes through said longitudinal axis X-X, 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 X-X. Finally, and unless otherwise specified, the terms "internal (or interior)" and "external (or exterior)", respectively, are used in reference to a radial direction so that the internal (i.e. radially internal) part or face d an element is closer to the longitudinal axis X-X than the external (i.e. radially external) part or face of the same element.

A rotor, such as a turbomachine rotor 2, is likely 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 X-X which is its axis of rotation. An imbalance is characterized in particular by a radial direction, a distance from the axis of rotation X-X of the rotor, and an intensity. It can, moreover, be measured according to different methods. For example, it is possible to measure the unbalance of the fan 21 by arranging one or more vibration sensors, such as accelerometers, at the level of one or more bearings of the low pressure shaft 27, the unbalance then being deducted at from overall models using measurements from vibration sensors. 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 X-X of the rotor.

Thus, rotor balancing requires precise knowledge of 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 casings 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 shaft 100 adapted to be mounted fixed on the rotor, extending along the longitudinal axis XX,
- a first flyweight 11 rotatably mounted on the support axis 100 around the longitudinal axis XX, and
- A second flyweight 12 rotatably mounted on the support axis 100 around the longitudinal axis XX.

The support shaft 100 is thus integral in rotation with the rotor around 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 X-X, the fact that the support axis 100 extends along the longitudinal axis X-X makes it possible to free from centrifugal forces exerted by the flyweights 11, 12 on the shaft 27 driving the rotor 21, 22, 27, 26 in rotation, and also extending along the longitudinal axis X-X. In any event, by varying the angular position of the two flyweights 11, 12 around the longitudinal axis X-X, it is possible to create a counter-unbalance varying between 0 and 2 times the individual unbalance of each flyweight 11, 12 .

In one embodiment, for example illustrated in FIG. 2, the dynamic balancing device 1 comprises a support 10 able to be fixedly mounted on the rotor, so as to be integral in rotation with the rotor. As seen in Figure 2, the support pin 100 has:
- a first end part 1001 protruding from a first surface of the support 10,
- A second end part 1002 protruding from a second surface of the support 10, opposite the first surface.

In this embodiment, the first flyweight 11 is rotatably mounted on the first end part 1001, and the second flyweight 12 is rotatably mounted on the second end part 1002.

Each of the first flyweight 11 and the second flyweight 12 is advantageously capable of being driven in rotation around the longitudinal axis X-X without interfering with the other of the first flyweight 11 and the second flyweight 12. This allows the dynamic balancing device 1 to provide finer unbalance correction, since the two flyweights 11, 12 can occupy the same angular position around the longitudinal axis X-X, without coming into abutment against each other. In other words, the counter-unbalance created can assume any angular position around the longitudinal axis X-X.

In the embodiment illustrated in FIG. 2, the first counterweight 11 is offset axially with respect to the second counterweight 12, that is to say that it is offset with respect to the second counterweight 12 along the axis longitudinal X-X. This is however not limiting, the first flyweight 11 and the second flyweight 12 being able to be arranged at the same position along the longitudinal axis X-X. 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 this -last can be driven in rotation around the longitudinal axis X-X without interfering with that of the first flyweight 11 and the second flyweight 12 which is dug. When the first flyweight 11 and the second flyweight 12 occupy the same position along the longitudinal axis X-X, their axial bulk is reduced.

In any case, as visible in Figures 3 and 4, each of the first flyweight 11 and the second flyweight 12 advantageously has the shape of a half-disk, 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 complementary shape 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 X-X, 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 flyweights 11, 12. In this case, the other flyweights may or may not be axially offset with respect to the first flyweight 11 and to the second flyweight 12, and/or be, or not, axially offset relative to each other. The additional weights make it possible in particular to correct imbalances taking 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 11, 12 comprise a material, for example Triamet® G19, which has a density of 18 tons per cubic meter. Each of the flyweights 11, 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 the unbalance 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 flyweight 11 in rotation, and
- a second motor 14 configured to drive the second weight 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 able to be fixedly mounted on a corresponding support 15, 16, the supports 15, 16 of the motors 13, 14 then being able to be fixed on the support 10 of the flyweights, 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. This is in fact an engine which can easily be made compact, which can prove to be particularly advantageous when the dynamic balancing device 1 is used within a model, of reduced dimensions.

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

In a preferred variant, the drive shaft 130, 140 of each of the first motor 13 and of the second motor 14 extends along the support shaft 10. This makes it possible to relieve the bearings (not shown) of the motors 13, 14 so that the support shaft 10 takes up the forces exerted by the flyweights 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) of the motors 13, 14 are flexible.

Alternatively, at least one of the first motor 13 and the second motor 14 drives the corresponding weight 11, 12 via a reduction mechanism (not shown). This makes it possible to generate a high torque on the flyweight 11, 12. In addition, this makes it possible to make the dynamic balancing device 1 irreversible. Indeed, the rotating forces seen by the flyweights 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 drive 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 flyweights 11, 12 could indeed generate an unbalance greater than the initial unbalance of the rotor. The presence of the reduction mechanism makes it possible to keep the flyweights 11, 12 in their position at the time of the breakdown, the time to carry out maintenance.

In one embodiment, the dynamic balancing device 1 can be controlled remotely. To do this, it typically comprises a computer (not shown). In addition, in order to ensure the control and the supply of electrical energy to the motors 13, 14 in a marker, it comprises a telemetry (not shown) which makes it possible to transmit signals between a rotating marker and a fixed marker, and comprises for example two rotary transformers, one for the electric power, and the other for the relay of the weak signals. In other embodiments, the electrical energy supply is ensured by accumulators (not shown) embedded in the dynamic balancing device 1, the commands being relayed by means of intangible media of the Wifi or Bluetooth type.

The dynamic balancing device 1 can typically be controlled in the following way.

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 command can for example consist of a counter-unbalance (or unbalance) objective, i.e. 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 by using the data supplied by the vibration sensors arranged at the level of the rotor bearings. It then controls the operation of the motors 13, 14 which rotate the flyweights 11, 12 around the longitudinal axis, and return the positions reached to the computer. By servo-control, the computer then refines the position of the flyweights 11, 12 in order to reach 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 disk corresponds to the intensity of the unbalance, the length of the stick corresponds to the distance of the unbalance from the longitudinal axis X-X, and the direction of the stick corresponds to the radial direction of the unbalance.

Advantageously, the dynamic balancing process E described is implemented during operation of the rotor, that is to say during rotation of the rotor relative to the housing 20 around the longitudinal axis X-X.

During 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 seen in Figure 3, the first weight 11 is first 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 11, 12 are rotated relative to each other so as to be positioned at 180° from each other (i.e. symmetrically opposite to each other with respect to the longitudinal axis), to within an angular aperture O.

Then, still with reference to Figure 3, the first flyweight 11 and the second flyweight 12 are rotated E2 simultaneously in phase with the first flyweight 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 flyweights 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 flyweights 11, 12 is in the same radial direction as the unbalance of the rotor.

During a second step, the intensity of the unbalance is sought and counterbalanced. To do this, as seen in Figure 4, the first flyweight 11 and the second flyweight 12 are rotated simultaneously 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 the intensity of the unbalance is compensated.
More specifically, the two weights 11, 12 are rotated with equal speeds but opposite directions of rotation until the dynamic situation of the rotor becomes weak, that is to say that the assembly formed by the rotor and the dynamic balancing device 1 has a total residual unbalance (ie sum of the initial unbalance of the rotor and the counter-unbalance formed by the two flyweights 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 XX.
In the case where it is a question of voluntarily unbalancing the rotor, that is to say where an unbalance greater than the initial unbalance of the rotor is sought, the flyweights 11, 12 are rotated simultaneously around the support axis 10, the first flyweight 11 being moved in phase opposition with the second flyweight 12, so as to increase the intensity of the initial unbalance, that is to say until the intensity of the unbalance worsens. 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 XX.

In the exemplary 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 dynamic balancing 1 can be arranged at any position within the low pressure body 21, 22, 27, 26.

Thanks to the device 1 and the dynamic balancing process E described, it is possible to adjust the balancing of a rotor without stopping the machine, or dismantling parts to gain access to the balancing zones and implement the adjustments. It is even possible to voluntarily 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 particularly advantageous for autonomously and automatically correcting the unbalance of a rotor, whether during maintenance, manufacturing, for example mass production, or test phases on said rotor. In any case, thanks to 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 the flyweights around the longitudinal axis. This is in particular simpler and more efficient than the unbalance determination methods known from the state of the art, where the unbalance is determined by reading the number and the radial position of the flyweights making it possible to wait for a fixed vibration situation.

In all that has been described previously, the turbomachine 2 is of the twin-spool, double-flow, direct-drive turbojet type. However, this is not limiting, since 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 reduction gear architecture, or a triple-body, double-flow turbomachine, whether these are models or real-size turbomachines.

Claims (11)

Dynamic balancing device (1) for a rotor, said rotor being rotatable relative to a casing around a longitudinal axis (XX), the device (1) comprising:
- a support shaft (100) suitable for being mounted fixed on the rotor, extending along the longitudinal axis (XX),
- a first weight (11) rotatably mounted on the support axis (100) around the longitudinal axis (XX), and
- a second counterweight (12) rotatably mounted on the support axis (100) around the longitudinal axis (XX). Device according to Claim 1, in which each of the first weight (11) and of the second weight (12) is capable of being driven in rotation around the longitudinal axis (X-X) without interfering with the other of the first flyweight (11) and the second flyweight (12). Device according to one of Claims 1 and 2, in which the first flyweight (11) is offset with respect to the second flyweight (12) along the longitudinal axis (X-X). Device according to claim 3, further comprising a support (10), the support pin (100) having:
- a first end part (1001) protruding from a first surface of the support (10),
- a second end part (1002) protruding from a second surface of the support (10), opposite the first surface,
- the first flyweight (11) being rotatably mounted on the first end part (1001), and
- the second flyweight (12) being rotatably mounted on the second end part (1002). Device according to one of Claims 1 to 4, further comprising:
- a first motor (13) configured to drive the first flyweight (11) in rotation, and
- a second motor (14) configured to drive the second flyweight (12) in rotation,
each of the first motor (13) and the second motor (14) being configured to be fixedly mounted on the rotor. Device according to claim 5, wherein at least one of the first motor (13) and the second motor (14) is an electric motor. Device according to one of Claims 1 to 6, in which the first counterweight (11) has a shape complementary to the second counterweight (12) so that, when the first counterweight (11) and the second counterweight (12) are positioned relative to each other with a predefined angular offset, around the longitudinal axis (X-X), the device (1) exerts no unbalance on the rotor. Turbomachine assembly (2) comprising:
- a casing (10),
- a rotor (21, 22, 27, 26) rotatable relative to the housing (10) around a longitudinal axis (XX), and
- a dynamic balancing device (1) for a rotor according to one of claims 1 to 7. Turbomachine (2) comprising an assembly according to claim 8. Dynamic balancing method (E) of a rotor, said rotor:
- being rotatable relative to a housing around a longitudinal axis (XX), and
- presenting an unbalance having a radial direction and an intensity,
the method (E) comprising steps of:
- rotation (E1) of a first counterweight (11) relative to a second counterweight (12) around a support axis (100) fixedly mounted on the rotor, and extending along the longitudinal axis ( XX), so that the first flyweight (11) and the second flyweight (12) occupy a common angular sector (A), and
- simultaneous rotation (E2) of the first flyweight (11) and the second flyweight (12) in phase with the first flyweight (11) around the support axis (100) so as to:
○ keep the common angular sector (A) constant, and
○ 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. Method according to claim 10, further comprising a step of simultaneously rotating (E3) the first flyweight (11) and the second flyweight (12), the first flyweight (11) being moved in phase opposition with the second weight (12) around the support axis (100) so as to:
- increase the common angular sector (A), and
- until the intensity of the unbalance is compensated.