EP3924639A1

EP3924639A1 - Device comprising a set of vibration absorbers, and vehicle equipped with such a device

Info

Publication number: EP3924639A1
Application number: EP20703255.8A
Authority: EP
Inventors: Kevin JABOVISTE; Gaël CHEVALLIER; Emeline SADOULET-REBOUL; Nicolas Peyret; Eric Collard; Charles ARNOULD
Original assignee: Centre National de la Recherche Scientifique CNRS; Thales SA; Universite de Franche-Comte
Current assignee: Centre National de la Recherche Scientifique CNRS; Thales SA; Universite de Franche-Comte
Priority date: 2019-02-11
Filing date: 2020-02-11
Publication date: 2021-12-22
Also published as: US11885391B2; IL285388A; US20220074460A1; FR3092634A1; WO2020165128A1; FR3092634B1

Abstract

The invention relates to a device (20) having a body (25) and a set of vibration absorbers (30) which are mounted on the body (25), each absorber (30) being movable with respect to the body (25) between a first position and a second position, each absorber (30) being able to oscillate with respect to the body (25) between its first and second position, a first natural frequency being defined for each absorber (30), at least one absorber (30) having a first natural frequency which differs from the first natural frequency of another absorber (30). Each absorber (30) has at least one deformation part (45) which is able to deform when the vibration absorber (30) oscillates between its first position and its second position, the deformation part (45) having at least two faces configured to rub against one another during the deformation of the deformation part (45).

Description

TITLE: Device comprising a set of vibration absorbers and vehicle equipped with such a device

The present invention relates to a device comprising an assembly of vibration absorbers. The present invention also relates to a vehicle equipped with such a device.

Devices mounted in mobile structures such as vehicles or fixed structures are frequently liable to move relative to the structure when subjected to stresses such as vibrations or shocks, for example because connecting parts between them. the device and the structure are not perfectly rigid or because the device itself is not perfectly rigid. As a result, when the structure itself is set in motion or is subjected to an impact, the device is frequently set in motion relative to the structure, a movement which is liable to have a large amplitude. This movement is, in particular, a vibration or oscillation, in which the device moves periodically or pseudo-periodically with respect to the structure around a position of equilibrium between two extreme positions of its movement. These extreme positions are particularly likely to depend on the level of external stresses and therefore to vary.

Such oscillatory movements have particularly strong amplitudes at specific frequencies called natural frequencies which are frequencies to which the device is particularly sensitive. Such oscillations are very detrimental for certain applications which require good control of the position or orientation of the device. For example, when the device contains a set of sensors or tools suitable for projecting, for example, a light ray or a directional beam of radiofrequency waves, the oscillations greatly reduce the measurement precision of the sensors or the spatial precision of the illumination. obtained. In addition, the oscillations participate in premature wear of the device since they cause the appearance in the various materials of repeated stresses, in particular because they are likely to last much longer than the stress which caused this oscillation.

It is frequently used dampers made of flexible polymers such as elastomers, interposed between the device and the supporting structure, the natural frequencies of which are sufficiently below the natural frequencies of the device to limit these oscillations and thus reduce their effects. However, the properties of elastomers are likely to vary greatly depending on the temperature, the frequency of the mechanical stresses to which they are subjected or the amplitude of these stresses. As a result, the ability of elastomeric dampers to effectively reduce the amplitude of the oscillations of the device varies greatly as a function of the temperature, and of the amplitude or frequency of these oscillations. In addition, the existence of natural frequencies of the dampers itself generates oscillations of the device.

It has been proposed to use sets of vibration absorbers, which are elements suspended from the body of the device and themselves capable of oscillating relative to the body of the device. By appropriate selection of the stiffnesses, damping rates and masses of these elements, it is possible to limit the amplitude of the oscillations of the device and to damp them quickly. In particular, vibration absorbers are frequently beams attached to the body of the device at one end, although other types of absorbers also exist. The absorber sets are notably tuned, that is to say their properties are chosen to best absorb the mechanical energy of the device.

However, these systems require great precision in the control of their properties, which is difficult since these properties depend mainly on the materials used. In particular, the damping and stiffness properties of prior art vibration absorbers are difficult to control. For example, the properties of elastomeric vibration absorbers vary with temperature.

There is therefore a need for a device having good damping and stiffness properties, these properties being stable over a wide range of temperatures and for a wide range of oscillation frequencies.

To this end, a device is provided comprising a body and a set of vibration absorbers mounted on the body, each vibration absorber being able to oscillate relative to the body between a first and a second position, a first natural frequency being defined for each resonator, at least one vibration absorber having a first natural frequency different from the first natural frequency of another vibration absorber, each vibration absorber comprising at least one deformation part capable of being deformed when the absorber of vibration oscillates between its first position and its second position, the deformation part having at least two faces configured to exert a shear force on one another during the deformation of the deformation part. Thanks to the invention, the properties of each vibration absorber, and in particular of the deformation part (s), are liable to be modified independently of the material used. In particular, the action of the shear faces against one another allows an increased dissipation of the mechanical energy linked to the movement of the body relative to the same part not comprising these faces. In addition, these properties vary little as a function of temperature and frequency of movements.

According to particular embodiments of the invention, the device comprises one or more of the following characteristics, taken in isolation or in any technically possible combination:

- The faces configured to exert a shear force on each other when the deformation part is deformed are configured to rub against each other as the deformation part is deformed.

- each deformation part comprises a stack of superimposed blades in a stacking direction, the deformation part extending in an elongation direction between a first end and a second end fixed to the body, the elongation direction being perpendicular to the stacking direction, the deformation part being configured to deform in bending upon oscillation of the vibration absorber, the bending causing a displacement of the first end in the stacking direction relative to the first end.

- Each deformation part further comprises at least one resin or elastomer layer interposed between two blades.

- Each deformation part has at least one rib interposed between two blades, each rib extending in a plane perpendicular to the stacking direction.

- Each deformation part comprises a reinforcing layer interposed between two blades, the reinforcing layer comprising a set of ribs, the set of ribs delimiting in particular, in a plane perpendicular to the stacking direction, a set of cells.

- Each vibration absorber includes a weight suspended from the body through the deformation part (s).

- the weight is able to move relative to the body in a direction of movement when the vibration absorber oscillates between its first and second positions, at least two deformation parts extending radially outward from the weight in the same plane perpendicular to the direction of movement. There is also proposed a vehicle equipped with a device as described above, the vehicle being in particular an aircraft.

According to particular embodiments of the invention, the vehicle comprises one or more of the following characteristics, taken in isolation or in any technically possible combination:

- the vehicle comprises a platform, the body being able to oscillate relative to the platform between a third position and a fourth position, a second natural frequency being defined for the body, the first natural frequency of at least one vibration absorber being strictly lower than the second natural frequency and the first natural frequency of at least one other vibration absorber being strictly greater than the second natural frequency.

- the body comprises a beam and a head, the beam having a third end and a fourth end and extending in a main direction between the third end and the fourth end, the fourth end being fixed to the platform, the body being able to oscillate relative to the platform between a third position and a fourth position, the head being fixed to the third end, each vibration absorber being mounted on the third end of the beam.

Characteristics and advantages of the invention will become apparent on reading the description which follows, given solely by way of non-limiting example, and made with reference to the accompanying drawings, in which:

[Fig 1] Figure 1 is a partial schematic representation of a vehicle equipped with a device comprising a set of vibration absorbers, each vibration absorber comprising at least one deformation part,

[Fig 2] Figure 2 is a schematic sectional view of an example of the deformation part of Figure 1,

[Fig 3] Figure 3 is a schematic sectional view of another example of the deformation part of Figure 1,

[Fig 4] Figure 4 is a schematic sectional view of another example of the deformation part of Figure 1,

[Fig 5] Figure 5 is a schematic sectional view of another example of the deformation part of Figure 1,

[Fig 6] Figure 6 is a schematic view of an example of the vehicle of Figure

1,

[Fig 7] FIG. 7 is a schematic perspective view of an example of a deformation part of FIG. 6, and [Fig 8] FIG. 8 is a schematic perspective view of an example of a vibration absorber comprising the deformation part of FIG. 7.

Several deformable parts are described in the description below. Unless otherwise indicated, the shapes of the parts are described when the part is at rest, free from any deformation. For example, a part described as being parallelepipedal or planar is parallelepipedic or planar when the part is not in motion but is stationary in the absence of external stress.

An example of vehicle 10 is partially shown in Figure 1.

The vehicle 10 is, for example, an aircraft such as an airplane or a helicopter.

As a variant, the vehicle 10 is a land vehicle, for example a wheeled vehicle, or else a tracked vehicle.

The vehicle 10 comprises a platform 15. The vehicle 10 is furthermore equipped with a device 20.

The platform 15 is a rigid structure suitable for maintaining in position the various elements which constitute the vehicle. For example, the platform is a frame on which are mounted in particular means for lifting or propelling the vehicle, such as an engine, wings or a rotor. As a variant, the platform is a rigid shell delimiting an internal compartment of the vehicle 10, for example a fuselage.

Device 20 is mounted on platform 15. For example, device 20 is attached to platform 15.

The device 20 comprises a body 25 and a set of vibration absorbers 30.

The body 25 comprises, for example, a set of functional organs 35 each capable of performing a function such as detection, measurement, emission or even projection.

At least one functional member 35 is, for example, an imager such as a camera or a photographic apparatus or a thermal camera, capable of generating an image from visible electromagnetic radiation, infra-red or even ultra-violet.

As a variant, at least one functional member 35 is a radar, or even a lidar. A radar (from the English "radio detection and ranging") is a system that uses electromagnetic waves to detect the presence and determine the position and speed of objects. A lidar (standing for “light detection and ranging” or “laser detection and ranging”) is a system which uses a light beam, in particular a beam visible laser, infra-red or ultra-violet to detect the presence and determine the position as well as the speed of objects.

According to another variant, at least one functional member 35 is a light projector, such as a headlight, capable of generating a light beam to illuminate objects around the vehicle 10.

According to another variant, at least one functional member 35 is an accelerometer or a gyrometer.

However, other examples of functional organs are also conceivable.

The body 25 is configured to support the functional member (s) 35 and to hold the functional member (s) 35 in position relative to the platform 15.

The body 25 is fixed to the platform 15. For example, the body 25 is fixed under the platform 15 when the vehicle 10 is in a position of usual use, for example when the vehicle 10 is moving in flight, is placed on the ground or moves on the ground. Alternatively, the body 25 is fixed above the platform 15, or even inside the platform 15

In the example shown in Figure 1, the body 25 is a parallelepiped fixed at one of its ends to the platform 15.

The body 25 extends in a main direction DP. The main direction is the direction in which the longest side of the parallelepiped extends.

However, it should be noted that the shape of the body 25 is liable to vary. The main direction DP is then the direction in which the body 25 has the longest dimension.

The body 25 is able to oscillate relative to the platform between two positions called third position and fourth position.

It is in particular understood by “oscillate” that the body 25 undergoes a periodic or pseudo-periodic movement, between the third position and the fourth position. This is symbolically represented by arrows 40 in Figure 1.

Note that, in other words, the body 25 oscillating "between the third position and the fourth position" is likely to be said to oscillate "around a first position of equilibrium".

The third and fourth positions are the extreme positions of the body's swinging motion 25.

The movement is, for example, an elastic deformation of the body 25 following a movement of the vehicle 10 or an impact undergone by the device 20 or by the vehicle 10. In particular, a part of the body 25 is set in motion relative to another part of the body 25, for example a free end 25A of the body 25 is moved relative to an end 25B of the body 25 fixed to the platform 15.

The end 25B is, for example fixed to the platform 15 by means of a fastener 42, or else is fixed directly to the platform 15.

For example, the body 25 is moved by shock or movement to its third position, the elasticity of the body 25 or fasteners 42 of the body 25 to the platform 15 causing the body 25 to move in its position. fourth position, the elasticity then causing the displacement to the third position, and so on. In particular, when the body is in one of the third and fourth positions, the elasticity tends to bring the body back to its position of equilibrium, called "first position of equilibrium", the inertia driving the body 25 towards the other of the third and fourth position.

The movement is said to be "periodic" if each movement of the body ends in the third position or in the fourth position at a fixed frequency. The movement is said to be "pseudo-periodic" if the amplitude or frequency of the movements varies with time, especially if the amplitude decreases with time. In the latter case, the third and fourth positions vary as a function of time.

According to the example of FIG. 1, the body 25 is able to deform in bending between the third and the fourth position in the direction represented by the arrows 40. A bending movement is, for example, a movement in which the body 25 wraps around an axis perpendicular to the main direction DP. For example, a movement in which each point of an external surface of the body 25 moves at all times in a direction parallel to an axis A, the axis A being perpendicular to one of the sides of the parallelepiped, is an example of flexion movement.

According to the example of Figure 1, the oscillation of the device 20 causes a displacement of the free end 25A relative to the end 25B along the axis A.

The axis A is in particular a vertical axis when the vehicle 10 is in operation.

A first natural frequency f01 is defined for the body 25. The first natural frequency f01 is the frequency at which the body 25 oscillates between the third and the fourth position when the body 25 is moved in one of the third and the fourth position. fourth position then left free to oscillate without a force being imposed on the body 25 to set it in motion. In other words, the first natural frequency f01 is the frequency at which the body 25 oscillates naturally without external constraint between the third and fourth positions.

The first natural frequency f01 is the inverse of a proper time period of the body 25, this proper time period being the time duration between the moment when the body 25 reaches its third position and the next moment when the body 25 reaches its third position after reaching its fourth position.

The term "first natural frequency" is used herein to identify a natural frequency of the body 25, while the term "second natural frequency" will be used below to identify a natural frequency of a vibration absorber 30. However, these terms do not define no order relation between these two natural frequencies, in particular does not imply that one is necessarily higher or lower than the other.

The first natural frequency f01 is between 10 Hertz (Hz) and 5000 Hz, for example between 100 Hz and 1000 Hz. It should be noted that the first natural frequency f01, and more generally each natural frequency, is likely to vary in temperature function.

In the example shown in Figure 1, the device 20 has 6 vibration absorbers 30. However, the number of vibration absorbers 30 is likely to vary.

Each vibration absorber 30 is mounted on the body 25. In particular, each vibration absorber 30 is supported by the body 25. Thus, each vibration absorber 30 is suspended from the platform 15 through the body 25. In particular, the vibration absorber 30 is not attached directly to the platform 15, nor is it in contact with the platform 15.

Each vibration absorber 30 is movable relative to the body 25 between a position called the first position and a position called the second position. Each vibration absorber 30 is able to oscillate between the first and the second position relative to the body 25.

It should be noted that, in other words, an absorber 30 oscillating "between the first and the second position" is likely to be said to oscillate "around a second equilibrium position".

More specifically, each vibration absorber 30 is configured to oscillate between the first and the second position when the body 25 oscillates between the third and the fourth position. In particular, each vibration absorber 30 is provided to move between the first and the second position in a direction identical to the direction in which the body 25 moves between the third and the fourth position. For example, each vibration absorber 30 is able to move along the axis A between the first and the second position.

However, the direction of movement of the vibration absorber 30 between the first and second position is likely to vary.

A second natural frequency f02 is defined for each vibration absorber 30.

The second natural frequency f02 of at least one vibration absorber 30 is different from the second natural frequency f02 of at least one other vibration absorber 30.

Each second natural frequency f02 is between 8 Hz and 6000 Hz. A difference is defined between each second natural frequency f02 and the first natural frequency f01 of the body 25. According to a particular embodiment, each difference is less than or equal to 20 percent. (%) of the first natural frequency f01, in particular less than or equal to 10 Hz. It should be noted that the frequency distribution of the second natural frequencies f02 is liable to vary. For example, as a variant, at least one difference is greater than or equal to 20% of the first natural frequency f01.

According to one embodiment, the second natural frequency f02 of at least one vibration absorber 30 is strictly greater than the first natural frequency f01 and the second natural frequency f02 of at least one vibration absorber 30 is strictly lower than the first natural frequency f01.

The second natural frequencies f02 are, for example, chosen to limit the amplitude of the oscillation of the body 25 relative to the platform 15 or the mechanical energy associated with the deformation of the body 25.

In particular, the vibration absorbers 30 form a vibratory trap device with distributed resonators (also known by the acronym “MTMD”, standing for “multiple tuned mass damper”), in which the vibration absorbers 30 are chosen for limit the amplitude of the oscillations of the body 25 and / or the mechanical energy associated with the deformation of the body 25.

The second natural frequencies f02 are, for example, chosen according to a frequency distribution law as mentioned in document US 2014/0008162 A1. Each vibration absorber 30 comprises at least one deformation part 45. Optionally, at least one vibration absorber 30 further comprises a weight 50.

According to the example of Figure 1, two of the vibration absorbers 30 each have a weight 50. As a variant, each vibration absorber 30 has a weight 50.

Each deformation part 45 is able to deform during the oscillation of the vibration absorber 30 between the first and the second position. In particular, each deformation part 45 has, when the vibration absorber 30 is in the first position, a shape different from the shape of the deformation part 45 when the vibration absorber 30 is in the second position.

Each deformation part 45 extends, for example, in a direction of elongation DE. According to the example of Fig. 1, each deformation piece 45 extends in the main direction DP, that is, the direction of elongation DE of each deformation piece 45 is the main direction DP.

Note that the direction of elongation DE is subject to change. For example, according to a possible variant, the direction of elongation DE is perpendicular to the axis A and to the main direction DP.

Each deformation part 45 has a first end 45A and a second end 45B. Each deformation piece 45 extends between the first end 45A and the second end 45B.

A length of the deformation piece 45, measured between the first and second ends 45A and 45B, is between 5 millimeters (mm) and 50 centimeters (cm). However, this length is likely to vary, in particular depending on the second natural frequency f02 desired for the vibration absorber 30 considered.

According to the example shown in Figure 1, the first end 45A is free and the second end 45B is fixed to the body 25.

Each deformation part 45 is, for example, capable of being deformed in bending during the oscillation of the vibration absorber 30. In particular, the first end 45A moves along the axis A between the first position and the second position.

According to one embodiment, each deformation part 45 is a plate perpendicular to the axis A. In particular, the plate extends in the main direction DP, that is to say that it has its largest dimension according to the main direction DP. On the contrary, the thickness of the plate is measured along the A axis, i.e. the smallest dimension of the plate is measured along the A axis. The plate has, for example, a rectangular shape in a plane perpendicular to the axis A. However, the shape of the plate is liable to vary.

Each deformation part 45 has faces 55, called “shear faces”, which are in particular visible in FIG. 2.

Each shear face 55 is configured to abut another shear face 55 as the strainer 45 deforms during oscillation of the vibration absorber 30. In particular, each shear face 55 is configured to exert. a shear force on the other shear face 55 against which it bears during oscillation of the vibration absorber 30. For example, each shear face 55 is configured to rub against the other shear face 55 .

The term "shear force" is understood to mean in particular a force directed in the plane formed, at the point of application of the force, by the faces 55 bearing against one another. Such a force appears in particular when a force tending to move one of the faces 55 in a direction of this plane is exerted by the other face 55.

A relative displacement between the shear faces 55 in the plane formed at the point considered by the shear faces 55 is an example of the relative movement of shear faces 55 capable of generating a stress force if the shear faces 55 rub against the shear faces 55. one against the other.

A shear force also appears when the face 55 on which the force is applied moves together with the other face 55. In this case, the shear force causes a deformation of the element in which the face 55 on which the force is applied. force is applied is spared, in order to accommodate the displacement of this face 55.

According to an embodiment shown in section in FIG. 2, the deformation part 45 comprises a stack of blades 60 superimposed in a stacking direction X. Optionally, the deformation part 45 further comprises at least one resin layer. 65. For example, a resin layer 65 is interposed along the stacking direction X between each pair of adjacent blades 60.

According to a variant, each layer 65 is an elastomer layer and not a resin layer.

The X stacking direction is, for example, parallel to the A axis.

The stacking direction X is, for example, perpendicular to the direction of elongation DE.

Each blade 60 extends in a plane perpendicular to the stacking direction x. Each blade 60 is, for example, made of a metallic material such as steel, in particular stainless steel. As a variant, each blade 60 is made of a composite material.

Each blade 60 has a thickness, measured in the stacking direction X, of between 10 microns (pm) and 5 mm, in particular between 25 pm and 200 pm. The blades 60 are, for example, fixed together at each end 45A, 45B of the deformation part by a bolt 70.

Alternatively, the blades 60 are kept attached to each other by the resin layers 65.

The blades 60 are, for example, provided to rub against each other during the deformation of the deformation part 45. For example, the shear faces 55 are the faces of the blades 60 which define the blades 60 in the direction of. stacking X. The shear faces 55 are, in particular, perpendicular to the direction of stacking X.

In particular, when the deformation part 45 is deformed by the oscillation of the vibration absorber 30, in particular when the first end 45A is moved relative to the second end 45B in the stacking direction X as indicated by the arrows 40 in FIG. 2, the shear faces 55 facing each other of the contiguous blades 60 rub against each other.

As a variant, during the deformation, one face of a blade 60 carries with it a face of a resin layer 65 which is in contact with the blade 60. In this case, the shear faces 55 are the faces of the blades. 60 and the faces of the resin layers 65. The displacement of the face of the resin layer 65 then causes the shear deformation of the resin layer 65.

According to the example shown in FIG. 2, each resin layer 65 extends over the entire length of the deformation part 45. In particular, each resin layer 65 is delimited in the direction of elongation DE by the two faces. of the deformation part 45 which delimits the deformation part 45 in the direction of elongation. Thus, a length of each resin layer 65, measured in the direction of elongation DE, is equal to the length of the deformation part 45.

However, embodiments in which at least one resin layer 65, in particular each resin layer 65, has a length less than the length of the deformation part 45, are also likely to be considered. Each resin layer 65 has a thickness, measured along the stacking direction X, less than or equal to 15 μm, for example between 0.5 μm and 1.5 μm.

Each resin layer 65 is made of a polymer material, for example of a polymer obtained by polymerization of epoxy monomers. Such a material is frequently referred to as an “epoxy resin”. It should be noted that the composition of the resin layers 65 is likely to vary from one layer to another.

According to another example of a deformation part 45, shown in FIG. 3, the deformation part 45 comprises a stack of blades 60 and at least one shear part 75 interposed between two blades 60. For example, the deformation part 45 comprises two blades 60 and a plurality of shearing parts 75 interposed between the two blades 60. According to possible variants, the deformation part 45 does not include a shearing part 75, or even comprises a single shearing part 75.

A single blade 60 among the blades 60 is, for example, fixed directly to the body 25, in particular to one of its ends, while the other blades 60 are not fixed to the body 25. According to one embodiment, the absorber of vibration 30 comprises a weight 50 fixed to a blade 60 which is not fixed to the body 25 while another blade 60 is fixed to the body 25.

As a variant, each blade 60 is directly attached jointly to the body 25 and to the weight 50.

Each blade 60 has a thickness, measured in the direction of stacking X, for example between 1 mm and 5 mm.

According to one embodiment, the shear pieces 75 are aligned with each other in the direction of elongation DE, for example the main direction DP.

In the example shown in Figure 3, the two blades 60 are attached to each other by bolts 80, for example 3 bolts 80.

Each shear piece 75 bears against the two blades 60 which surround it in the stacking direction X.

Each shear piece 75 is, for example, a plate, in particular a metal plate. According to one embodiment, the shearing part 75 is made of steel. However, the material in which the shear piece 75 is made is likely to vary.

Each shear piece 75 is perpendicular to the stacking direction X. The shear piece 75 has a thickness, measured along the stacking direction X, for example between 1 mm and 5 mm.

The shear piece 75 has a length, measured in the direction of elongation DE, of between 2 mm and 50 cm.

According to the embodiment of FIG. 3, each floating piece 75 corresponds to a bolt 80, the shear piece 75 being crossed by the corresponding bolt 80.

Each bolt 80 successively passes through a blade 60, the corresponding shear piece 75 and the other blade 60.

According to one embodiment, at least one bolt 80 is loosened with respect to the maximum possible tightening for the bolt 80 considered. For example, a single bolt 80 among bolts 80 is tightened to the maximum while the other bolts 80 are tightened to the maximum and then loosened from the maximum tightness. In particular, the other bolts 80 are loosened from the maximum tightening by a number of turns between a tenth of a turn and a turn and a half.

During oscillation of the vibration absorber 30, the shear piece 75 rubs against the blades 60. Thus, the shear faces 55 are the faces of the blades 60 and of the shear pieces 75 which are perpendicular to the direction of. 'X stacking.

According to a third example of a deformation part 45, shown in FIG. 4, the deformation part 45 comprises a stack of blades 60 superimposed in a stacking direction X, similar to the stack of the first and second examples, and at least a rib 85.

For example, the deformation part 45 comprises a reinforcing layer 87 interposed in the stacking direction X between two contiguous blades 60, as shown in FIG. 4. The reinforcing layer 87 comprises a plurality of ribs 85.

In the example shown in FIG. 4, the deformation part 45 comprises two blades 60. However, embodiments in which the deformation part 45 comprises more than two blades 60 and at least two reinforcing layers 87 are also possible. .

Each rib 85 extends in a plane perpendicular to the stacking direction X.

Each rib 85 extends, for example, in the direction of elongation DE or in a direction perpendicular to the direction of elongation DE and to the direction of stacking X. As a variant, certain ribs 85 extend in a direction. forming an angle other than 90 degrees with the direction of elongation DE. According to the example shown in FIG. 4, the ribs 85 define a set of cells 88 in the reinforcing layer 87. In particular, each cell 88 is delimited in a plane perpendicular to the stacking direction X by the ribs 85 It should be noted that embodiments in which the ribs 85 do not define cells, for example if the ribs 85 are all parallel to one another, can also be envisaged.

Each rib 85 has a thickness, measured along the stacking direction X, for example between 1 mm and 5 mm.

Each cell 88 has dimensions, measured in a plane perpendicular to the stacking direction X, for example between 5 mm and 50 mm.

It should be noted that the dimensions of the cells 88 are liable to vary.

According to one embodiment, the cells 88 are identical to one another. As a variant, the cells 88 of the same deformation part 45 are liable to differ from each other. For example, at least one dimension of the cells 88 varies between the first end 45A and the second end 45B.

Each rib 85 bears against a shear face 55 of each blade 60 between which the rib 85 is interposed in the stacking direction X.

According to one embodiment, the reinforcing layer 87 is configured to allow relative movement between the blades 60 bearing against the reinforcing layer 87 and the reinforcing layer 87.

The reinforcing layer 87 is, for example, fixed to the adjacent blades 60 at the level of the ends 45A and 45B of the deformation part 45, for example by bolts, or else by gluing, but at least a portion of the reinforcing layer 87 disposed between the ends 45A and 45B is not attached directly to the blades 60, so that relative movement between the blades 60 and the reinforcing layer 87 is possible at this portion.

Thus, during the oscillation of the vibration absorber 30, the shear faces 55 of the blades 60 rub against the faces of the reinforcing layer 87 against which they bear, these faces then also playing the role of faces of shear 55.

As a variant, the shear faces 55 of the blades 60 are integral with the faces of the layer 87 against which they bear, the deformation of the deformation part 45 then causing a shear deformation of the reinforcing layer 87. According to a fourth example of a shear piece 45, shown in FIG. 5, the deformation piece 45 is in one piece.

For example, the deformation part 45 is a plate extending in a direction of elongation DE and perpendicular to an X direction along which the thickness of the plate is measured. For example, the direction of elongation DE is the main direction DP and the direction X is parallel to the axis A.

As a variant, the deformation part 45 is a beam. However, other forms of deformation parts 45 are conceivable.

The deformation part 45 is, for example, made of a metallic material, in particular steel, stainless steel or aluminum. As a variant, the deformation part 45 is made of a polymer material, or else of a composite material.

The deformation part 45 comprises slots 90. Each slot 90 is formed, for example machined, in the deformation part 45.

Each slot 90 is, for example, delimited by two flat shear faces 55 formed in the deformation part 45. Each slot 90 opens, in particular, on at least one face of the deformation part 45.

According to the example shown in Figure 5, each slot 90 opens onto a face perpendicular to the X direction and on the two side faces which are parallel to the direction of elongation DE and to the direction X.

Each slot 90 extends, for example, in a plane perpendicular to a normal direction N included in a plane comprising the direction of elongation DE and the direction X. It should be noted that the slots 90 having a curvilinear profile, c ' that is to say in which the normal direction N varies from one point to another, are also possible.

An angle between the direction of elongation DE and the normal direction N is, for example, greater than or equal to 30 degrees (°), for example between 30 ° and 60 °.

Note that the orientation of the slots 90 is subject to change. For example, the angle between the direction of elongation DE and the normal direction N is likely to vary from slot 90 to slot.

Each slot 90 has a width, measured in the normal direction N between the two shear faces 55 of the slot 90, for example between 0.01 mm and 5 mm.

It should be noted that the width of the slots 90 is liable to vary, in particular depending on the dimensions of the deformation part 45 and the amplitude of the oscillations of this deformation part 45. Each slot 90 has a depth P, measured in a plane perpendicular to the normal direction N, from a surface of the deformation part 45, for example between 20 μm and 5 cm.

The number of slots 90 is, in particular, chosen according to the properties desired for the vibration absorber 30.

During the deformation of the deformation part 45, the shear faces 55 of certain slots 90 are brought together until they are pressed against each other. The resulting friction therefore participates in the dissipation of mechanical energy, and thus in the damping of the oscillation of the body 25.

As mentioned previously, each of the deformation parts 45 described above is likely to belong to a vibration absorber 30 comprising a weight 50.

Each weight 50 is supported by the deformation part (s) 45 of the vibration absorber 30 considered. In particular, each weight 50 is connected by the deformation part or parts 45 to the body 25.

Each weight 50 is suspended from the body 25 through the deformation part or pieces 45. In particular, the weight 50 is not attached directly to the body 25, and is not in contact with the body 25.

Each weight 50 has a mass. The mass of the weight 50 is chosen so that the second natural frequency f02 of the vibration absorber 30 in question has a predefined value. For this, the shape, material and volume of each flyweight 50 are likely to vary from one flyweight 50 to another.

When body 25 oscillates between the third and fourth position, the vibration absorbers 30 are set in motion relative to the body 25. Thus, part of the mechanical energy of the system is directed into the oscillation modes of the absorbers. vibrations 30 and not in the mode or modes of oscillation of the body 25. The amplitude of the oscillations of the body 25 is therefore reduced.

Thanks to the use of shear faces 55 in the deformation part 45, it is possible to vary the properties of the vibration absorbers 30, in particular to choose the desired values of the damping rate of the vibration absorber 30, or the stiffness of the vibration absorber 30. In particular, it is possible to vary these properties independently of the materials used, in particular by modifying the number or the area of the shear faces 55, or even the bearing force between these shear faces 55. This is all the more interesting as the damping rate is generally a difficult parameter to control for the vibration absorbers of the state of the art.

The shear faces 55 in particular allow greater dissipation of the mechanical energy associated with the oscillation movement of the body 25, and therefore faster damping of this movement. In fact, these shear faces 55 exert a shear force on one another making it possible to dissipate energy via the friction of the shear faces against one another and / or via the deformation resulting from the shear. .

The properties of the deformation parts 45 are then likely to vary over a wider range than the vibration absorbers of the prior art which do not have shear faces 55 and which are therefore limited by the properties of the materials used.

The damping rate is a dimensionless quantity characterizing the evolution and the decrease over time of the oscillations of a physical system. The damping rate is frequently defined as being equal to the ratio of the maximum energy dissipated during a period of oscillation and the maximum energy of deformation of the system considered during this same cycle.

The stiffness expresses the relation of proportionality between the force F applied at a point and the resulting deflection x at this point. It is in particular equal to the ratio between the force F and the deflection x.

In addition, the mechanical behavior of the vibration absorbers 30, and therefore their ability to limit the amplitude of the oscillations of the device 20, varies little as a function of the temperature and the frequency of these oscillations, since the mechanical properties of the friction between the shear faces 55 are very stable. In particular, the damping rate and stiffness vary very little with temperature.

A deformation part 45 comprising superposed blades 60 can be easily adapted to obtain the desired properties by simply varying the number of blades 60 used. In particular, the stiffness, mass and damping properties of such a strainer 45 vary greatly depending on the number of blades 60 when considering a flexural strain of the strainer 45.

The presence of the resin layer 65 between the blades 60 makes it possible to fix the blades 60 together while allowing relative movement between them so as to allow friction between the blades 60 during the oscillation while preserving the integrity. of the deformation part 45. In addition, it is easy to manufacture stacks of blades 60 interconnected by resin layers 65, and to adapt the properties of the deformation part 45 thus obtained by removing the blades 60, in particular by hand, until to obtain the desired properties. The deformation parts 45 are then very adjustable, and can in particular be adapted to modifications of the natural frequency f01 (for example if functional members 35 are modified or added to the device 20) without additional equipment.

The stiffness and the damping rate of a deformation part 45 comprising one or more shear parts 75 bolted to the blades 60 can in particular be easily modified and adapted by modifying the tightening of the bolts 80.

The use of ribs 85 also makes it possible to vary the stiffness properties of the deformation part 45, in particular when the number or the dimensions of the ribs 85 and of the cells 88 which they define vary, for example of a deformation part. 45 to the other.

The use of weights 50 makes it possible to adapt the mass of the vibration absorber 30 and thus to modify the second natural frequency f02 of the vibration absorber 30, without modifying the stiffness or the damping rate of the absorber. vibration absorbers 30. It is thus easier to obtain a set of vibration absorbers 30 having properties, and in particular stiffnesses, masses and damping rates, allowing optimal damping of the movement of the body 25.

A second example of vehicle 10, shown in FIG. 6, will now be described. The elements identical to the first example of vehicle 10 are not described again. Only the differences are highlighted.

The body 25 includes a support 95 and a head 100 which contains the functional organs 35.

The support 95 is, for example, a beam, as shown in FIG. 6. As a variant, the support 95 is a plate, or yet another type of structure making it possible to suspend the head 100 from the platform 15.

The support 95 extends in the main direction DP.

The support 95 has a third end 95A and a fourth end

95B.

The support 95 is, for example, a beam with a square or rectangular section. In particular, each side of the support 95 is perpendicular either to the main direction DP or to the A axis or to a direction perpendicular to the A axis and to the main direction DP.

The third end 95A is free. The head 100 is fixed to the third end 95A, for example under the third end 95A when the vehicle 10 is in operation.

The fourth end 95B is fixed to the platform 15. For example, the fourth end 95B is fixed to the platform 15 by means of one or more fasteners 102, or else fixed directly to the platform. shape 15.

The support 95 is able to deform in bending when the body 25 oscillates between the third and the fourth position in the direction represented by the arrows 40. According to the example of FIG. 6, the oscillation of the device 20 causes a displacement of the free end 95A relative to the end 95B along the axis A.

Each vibration absorber 30 is fixed to the third end 95A of the support 95.

According to the example shown in Figure 6, each vibration absorber 30 is accommodated in an opening 105 formed in the third end 95A of the support 95.

Each opening 105 extends along the axis A along which the third end 95A moves relative to the fourth end 95B during the bending of the support 95. Each opening 105 is, for example, cylindrical, that is to say. say that it has a circular section in a plane perpendicular to the axis A and has a constant diameter. However, the shape of the opening 105 is likely to vary.

Alternatively, the opening 105 has a shoulder delimiting a first section and a second section of different diameter from the first section.

Each opening 105 opens onto at least one face of the support 95, for example each opening opens at each of its two ends on one face of the support 95. In Figure 6, the opening 105 opens at both ends. It should be noted that cases where the opening 105 only opens at one of its ends are also possible.

Each vibration absorber 30 comprises at least one deformation part 45 and a weight 50.

Each deformation part 45 is provided to allow movement of the corresponding weight 50 in a direction of movement, which is for example parallel to the axis A.

For example, each weight 50 is supported by at least two deformation parts 45 which surround the weight 50 in a plane perpendicular to the direction of movement of the weight 50. According to the example of FIG. 6, each vibration absorber 30 comprises at least two groups of deformation parts 45, these groups being offset with respect to one another along the axis A.

Each group of deformation parts 45 is a set of deformation parts extending in the same plane perpendicular to the direction of movement of the weight.

For example, each group is a deformation element 1 12 comprising at least two deformation parts 45.

The deformation element 1 12 is, for example, such that the deformation pieces 45 of the deformation element 1 12 are integrally formed with each other. For example, the deformation parts 45 comprise a single stack of blades 60 as shown in any one of FIGS. 2 to 4, the blades 60 having, in a plane perpendicular to the stacking direction X, a shape suitable for defining several deformation parts 45.

As a variant, the deformation pieces 45 of the deformation element 1 12 are fixed to one another without having come from the material, or the deformation parts 45 of the same group are not fixed to each other. other.

A deformation element 1 12 comprising three deformation parts 45 is shown in Figure 7.

It should be noted that the number of deformation pieces 45 of each group is liable to vary.

The deformation pieces 45 of the same group extend radially outwards from the flyweight 50 in a plane perpendicular to the direction of movement of the flyweight 50. This can be seen in particular in Figure 8.

It is in particular understood by "radially outwards" that each deformation part extends along a clean line, the clean lines being concurrent with one another at a point, this point being accommodated in the weight 50.

The deformation element 1 12 comprises for example an inner ring 1 15 and an outer ring 120 concentric and coplanar, each deformation part 45 extending radially from the inner ring 1 15 to the outer ring 120 Thus, the first end 45A is fixed to the inner ring 115 and the second end 45B is fixed to the outer ring 120.

It should be noted that according to one possible embodiment, the internal 1 15 and external 120 rings are each capable of extending in a plane distinct from the plane in which the other ring 1 15, 120 of the same group of deformation parts 45. This allows in particular to pre-stress the group of deformation parts 45 and therefore to modify the stiffness and / or the damping rate of the vibration absorber 30.

The internal ring 1 15 has a diameter, for example greater than or equal to

2 mm.

The outer ring 120 is fixed to the body 25, in particular to the walls of the support 95 which define the opening 105 in which the vibration absorber 30 is accommodated.

The outer ring 120 has a diameter greater than or equal to, for example, 5 mm.

It should be noted that, although the rings 115 and 120 are shown in FIG. 7 as being rings with a circular base, that is to say rings delimited in a plane perpendicular to the direction of movement by circles concentric, it is conceivable that these rings 115 and 120 are rings with a polygonal base delimited by polygons having a homothety relationship between them, or else rings with any base.

Each weight 50 extends along an axis B which is parallel to the direction of travel. In particular, the B axis includes the centers of the internal 1 15 and external 120 rings of each deformation element 1 12.

In particular, the weight 50 has a symmetry of revolution about the axis B. Each weight 50 is, for example, cylindrical. The weight 50 then has a diameter greater than or equal, for example, to 3 mm. In particular, the diameter of the flyweight 50 is between the diameter of the inner ring 1 15 and the diameter of the outer ring 120.

As a variant, each weight 50 is parallelepiped, or else has any section. In this case, each section of the weight in a plane perpendicular to the B axis has a center of gravity, the center of gravity being, for example, a point on the B axis. The center of gravity is, for example, the intersection of the diagonals of the section when the section is rectangular.

In the example shown in FIG. 8, the centers of gravity of the different sections of the weight are aligned along the axis B. According to a possible variant, the centers of gravity of the different sections of the weight 50 may not be. not aligned along the B axis, for example if the centers of gravity are not aligned with each other.

This makes it possible in particular to promote the appearance of other modes of vibration of the vibration absorber 30, which participate in improving the damping of the body 25. The weight 50 is fixed to the internal ring 1 15. In particular, the internal ring 1 15 of each deformation element 1 12 is received in the weight 50, as shown in FIG. 8. For example, the weight 50 is consisting of at least two separate parts aligned in the direction of movement and between which the internal ring 1 15 is interposed.

Many means are possible to fix the weight to the deformation elements 1 12, in particular the fixing by one or more bolts.

During the oscillation of the vibration absorber 30, the weight 50 moves along the axis B inside the opening 105. This movement causes the bending deformation of each deformation part 45, in particular via a displacement along the axis B of the first end 45A relative to the second end 45B.

The vibration absorbers 30 shown in FIGS. 6 to 8 allow effective damping of the oscillations of the body 25, in particular a reduction in the amplitude of these oscillations, without increasing the volume or the dimensions of the body 25. In addition, these absorbers of vibrations 30 are easily adaptable, for example by replacing the weight 50 with a weight 50 of different mass.

It should be noted that such vibration absorbers 30, although they have been described as being integrated into a device 20 whose body 25 comprises a support 95, in particular a beam 95, and a head 100, are likely to be used in other types of devices 20.

It should also be noted that embodiments in which the vibration absorbers 30 conform to any one of the examples of vibration absorbers of Figures 1 to 5 are also conceivable.

It should also be noted that only one mode of oscillation of the body 25 has been described above, that is to say an oscillation in a single direction at a single natural frequency f01, however several modes of oscillation of the body 25. bodies 25 can be envisaged, each mode corresponding to a distinct set of vibration absorbers 30, the vibration absorbers 30 corresponding to an oscillation mode being in particular configured to move between their first and second positions in a direction different from the direction corresponding to the other modes and / or to oscillate with natural frequencies f02 different from the natural frequencies f02 of the vibration absorbers 30 corresponding to the other oscillation modes.

In addition, the movements of the body 25 and of the deformation parts 45 have previously been described as bending movements. However, cases where the body 25 and the deformation parts 45 undergo movements other than flexures during the oscillation of the body 25 and vibration absorbers 30 are also possible, for example modes of torsion, or even tilting.

Furthermore, the oscillations of the body have been described above as being linked to a deformation of the body 25, in particular a bending. However, cases where the oscillation is caused by elastic deformation of the fastener (s) 42, 102 are also conceivable.

Claims

1. Device (20) comprising a body (25) and a set of vibration absorbers (30) mounted on the body (25), each vibration absorber (30) being able to oscillate relative to the body (25) between a first and a second position, a first natural frequency being defined for each vibration absorber (30), at least one vibration absorber (30) having a first natural frequency different from the first natural frequency of another vibration absorber ( 30),

each vibration absorber (30) comprising at least one deformation part (45) capable of deforming when the vibration absorber (30) oscillates between its first position and its second position, the deformation part (45) having at least two faces (55) configured to exert a shear force on one another during the deformation of the deformation part (45), the faces (55) configured to exert a force of shear upon deformation of the deformation part (45) being configured to rub against each other upon deformation of the deformation part (45).

2. Device according to claim 1, wherein each deformation part (45) comprises a stack of blades (60) superimposed in a stacking direction (X), the deformation part (45) extending in a direction of 'elongation (DE) between a first end (45A) and a second end (45B) fixed to the body (25), the direction of elongation (DE) being perpendicular to the direction of stacking (X), the deformation part (45) being configured to deform in flexion upon oscillation of the vibration absorber (30), the flexion causing displacement of the first end (45A) in the stacking direction (X) with respect to the second end (45B).

3. Device according to claim 2, wherein each deformation part (45) further comprises at least one resin layer (65) or elastomer interposed between two blades (60).

4. Device according to claim 2 or 3, wherein each deformation part (45) comprises at least one rib (85) interposed between two blades (60), each rib (60) extending in a plane perpendicular to the direction. stacking (X).

5. Device according to claim 4, wherein each deformation part (45) comprises a reinforcing layer (87) interposed between two blades, the reinforcing layer (87) comprising a set of ribs (85), the set of ribs (85) delimiting in particular, in a plane perpendicular to the stacking direction (X), a set of cells (60).

6. Device according to any one of claims 1 to 5, wherein each vibration absorber (30) comprises a weight (50) suspended from the body (25) via the part (s) of deformation ( 45).

7. Device according to claim 6, wherein the weight (50) is able to move relative to the body (25) in a direction of movement when the vibration absorber (30) oscillates between its first and second positions, at the at least two deformation pieces (45) extending radially outwards from the flyweight (50) in the same plane perpendicular to the direction of movement.

8. Vehicle (10) equipped with a device according to any one of claims 1 to 7, the vehicle (10) being in particular an aircraft.

9. Vehicle (10) according to claim 8, comprising a platform (15), the body (25) being adapted to oscillate relative to the platform (15) between a third position and a fourth position, a second natural frequency being defined for the body, the first natural frequency of at least one vibration absorber (30) being strictly lower than the second natural frequency and the first natural frequency of at least one other vibration absorber (30) being strictly greater than the second natural frequency.

10. Vehicle according to claim 8 or 9, wherein the body (25) comprises a beam (95) and a head (100), the beam (95) having a third end (95A) and a fourth end (95B) and extending in a main direction (DP) between the third end (95A) and the fourth end (95B), the fourth end (95B) being fixed to the platform (15), the body (25) being specific to oscillate relative to the platform (15) between a third position and a fourth position, the head (100) being fixed at the third end (95A), each vibration absorber (30) being mounted on the third end (95A) of the beam (95).