Sound-absorbing structure comprising a honeycomb structure and at least one partition tube having at least two flat spots connected to the walls of the honeycomb structure

Abstract

The invention relates to an acoustic absorption structure comprising at least one alveolar structure, interposed between an acoustically resistive layer and a reflective layer, which comprises a multitude of cells (60) as well as at least one partition tube (62) positioned in one of the cells (60) and configured to delimit in the cell (60) two cavities forming two resonators, the partition tube (62) comprising at least two flats (72, 72'), the walls which delimit the cell (60) in which the partition tube (62) is inserted comprising at least first and second planar fixing walls against which the flats (72, 72') of the partition tube (62) are pressed and fixed as well as at least two distant walls spaced from the side wall (74) of the partition tube (62).

Description

[0001] The present application relates to an acoustic absorption structure comprising a honeycomb structure and at least one partition tube which has at least two flats connected to walls of the honeycomb structure.

[0002] According to an embodiment of the prior art, an aircraft propulsion assembly comprises a nacelle and a dual-flow turbomachine, positioned inside the nacelle, which has, at the rear, a primary exhaust duct through which the burnt gases resulting from the combustion are evacuated. This primary exhaust duct comprises, at its skin, an acoustic absorption structure to attenuate noise on several frequency bands, such as for example noises linked to combustion (300-1000 Hz) and noises linked to the operation of the turbine (greater than or equal to 4000 Hz).

[0003] According to a first embodiment, an acoustic absorption structure comprises at least one honeycomb structure positioned between an acoustically resistive layer in contact with a medium in which acoustic waves propagate and a reflective layer. This embodiment makes it possible to obtain a ¼ wave resonator suitable for attenuating sound waves with high frequencies. According to this embodiment, the frequency range of the attenuated sound waves depends on the height of the cells of the honeycomb structure.

[0004] According to a second embodiment visible on the figure 1 and described in document FR094668, an acoustic absorption structure 10 comprises first and second alveolar structures 12, 14 positioned between an acoustically resistive layer 16 in contact with a medium in which acoustic waves propagate and a reflective layer 18. This acoustic absorption structure 10 comprises a separation layer 20 interposed between the first and second alveolar structures 12, 14, the first alveolar structure 12 being interposed between the acoustically resistive layer 16 and the separation layer 20, the second alveolar structure 14 being interposed between the reflective layer 18 and the separation layer 20.

[0005] According to this second embodiment, the separation layer 20 comprises orifices 22 allowing the cells of the first alveolar structure 12 to communicate with those of the second alveolar structure 14, each orifice 22 being extended by a tube 24 positioned in the second alveolar structure 14.

[0006] The acoustic absorption structure 10 makes it possible to obtain two types of resonators, a first Helmholtz type resonator at the level of the cells of the first alveolar structure 12, adapted to attenuate low-frequency sound waves, as well as a second ¼-wave type resonator at the level of the cells of the second alveolar structure 14, adapted to attenuate high-frequency sound waves.

[0007] According to this second embodiment, each tube 24 is connected by a connection 24.1 to the separation layer and then the first and second alveolar structures 12, 14 are connected by connections 12.1, 14.1 to the separation layer 20. The cells of the first and second alveolar structures 12, 14 must be perfectly aligned so that each cell of the first alveolar structure 12 communicates with only one cell of the second alveolar structure 14.

[0008] Even if this second embodiment makes it possible to attenuate the sound waves over wider frequency ranges, it is not fully satisfactory because the large number of connections leads to an increase in the mass of the sound absorption structure 10 and to a complication of its manufacturing process. The latter is all the more complex to implement since the cells of the first and second alveolar structures must be perfectly aligned to obtain optimal operation. According to another drawback, such a sound absorption structure requires at least two drainage systems, one for each of the first and second alveolar structures 12, 14, which tends to complicate the sound absorption structure. Finally, shaping the sound absorption structure 10 according to a curved profile proves difficult given the connections 12.1, 14.1 which connect the ends of the walls delimiting the cells of the first and second alveolar walls 12, 14 with the separation layer 20.

[0009] The present invention aims to remedy all or part of the drawbacks of the prior art.

[0010] To this end, the invention relates to an acoustic absorption structure comprising at least one alveolar structure interposed between an acoustically resistive layer and a reflective layer, the alveolar structure comprising a first face in contact with the acoustically resistive layer, a second face in contact with the reflective layer as well as a multitude of cells each opening at the level of the first and second faces, each cell being delimited by walls.

[0011] According to the invention, the cellular structure comprises at least one partition tube, positioned in one of the cells, comprising a first duct which extends between first and second ends and has a first section between the first and second ends, a second duct which extends between first and second ends and has a second section between the first and second ends, the second section being smaller than the first section, as well as a junction wall connecting the second ends of the first and second ducts; the first end of the first duct being closed by a first layer among the acoustically resistive layer and the reflective layer, the first end of the second duct being spaced from a second layer, different from the first layer, among the acoustically resistive layer and the reflective layer.In addition, the first conduit of the partition tube comprises at least two flats and at least one side wall, the walls which delimit the cell in which the partition tube is inserted comprising at least first and second flat fixing walls against which the flats of the partition tube are pressed and fixed as well as at least two distant walls spaced from the side wall of the partition tube.

[0012] This solution provides a honeycomb structure comprising two types of resonators configured to attenuate sound waves over a wide frequency band or over several frequency bands. Providing a partition tube that includes at least two flats fixed against first and second flat walls of the cell simplifies the fixing of the partition tube, provides better strength to the connection connecting the partition tube and the honeycomb structure and allows the honeycomb structure to retain a certain flexibility to conform it.

[0013] According to another characteristic, the sound absorption structure comprises at least a first drainage network which comprises first and second openings passing through the first and second fixing walls as well as at least a second drainage network which comprises third and fourth openings passing through third and fourth walls opposite the first and second fixing walls.

[0014] According to another characteristic, each wall of the cell in which the partition tube is positioned comprises first and second end edges located at the first and second faces of the honeycomb structure. In addition, the first, second, third and fourth openings are located at the first or second end edges of the walls at which the first end of the first conduit of the partition tube is positioned.

[0015] According to another feature, the partition tube comprises at least one notch which extends from the first end of the first conduit, said notch being configured to clear at least the first and second openings when the partition tube is fixed to the first and second fixing walls.

[0016] According to another feature, the partition tube comprises a single notch which clears the first and second openings.

[0017] According to another characteristic, the notch is delimited by a first edge as well as second and third edges, connecting the first edge and the upper end of the first conduit, distant from the side wall.

[0018] According to another characteristic, the first and second fixing walls are connected by a common lateral edge, the partition tube comprising an intermediate zone which separates the two flats, spaced from the lateral edge common to the first and second fixing walls.

[0019] According to another characteristic, each flat extends from the first end to the second end of the first conduit.

[0020] According to another characteristic, the side wall comprises two plane parts parallel to each other and connected to the flats as well as a curved part connecting the two plane parts, the plane and curved parts of the side wall being spaced from the walls of the cell in which the partition tube is positioned.

[0021] According to another characteristic, in a given area, each cell of the cellular structure comprises a partition tube connected to first and second fixing walls crossed by first and second openings and spaced from third and fourth walls opposite the first and second fixing walls and crossed by third and fourth openings. In addition, the first and second fixing walls of the cells are connected to each other so as to form, in top view, at least a first broken line, the partition tubes being positioned on either side of the first broken line and connected to the first and second fixing walls, the third and fourth walls of the cells being connected to each other so as to form, in top view, at least a second broken line spaced from the first broken line.

[0022] Other characteristics and advantages will emerge from the description of the invention which follows, a description given by way of example only, with reference to the appended drawings, among which: [ Fig. 1 ] is a schematic section of an acoustic absorption structure illustrating an embodiment of the prior art, [ Fig. 2 ] is a side view of an aircraft, [ Fig. 3 ] is a longitudinal section of a part of an aircraft propulsion system, [ Fig. 4 ] is a longitudinal section of a portion of a sound-absorbing structure illustrating one embodiment of the invention, [ Fig. 5 ] is a longitudinal section of a portion of a sound-absorbing structure illustrating another embodiment of the invention, [ Fig. 6 ] is a schematic representation of the different stages of a method of manufacturing an acoustic absorption structure illustrating an embodiment of the invention, [ Fig. 7 ] is a schematic representation of the different stages of a method of manufacturing an acoustic absorption structure illustrating another embodiment of the invention, [ Fig. 8 ] is a side view of a partition tube without a notch illustrating an embodiment of the invention, [ Fig. 9 ] is a perspective view of the partition tube visible on the figure 8 , [ Fig. 10 ] is a top view of the partition tube, visible on the figure 8 , positioned in a cell of a honeycomb structure illustrating an embodiment of the invention, [ Fig. 11 ] is a side view of a part having two partition tubes illustrating an embodiment of the invention, [ Fig. 12 ] is a side view of a partition tube illustrating one embodiment of the invention, [ Fig. 13 ] is a perspective view of the partition tube visible on the figure 12 , [ Fig. 14 ] is a perspective view of a cell of a honeycomb structure and a partition tube, before and after assembly, illustrating an embodiment of the invention, [ Fig. 15 ] is a perspective view of several cells of a honeycomb structure and several partition tubes, in the process of being assembled, illustrating an embodiment of the invention, [ Fig. 16 ] is a perspective view of a portion of a honeycomb structure illustrating one embodiment of the invention.

[0023] On the figure 2 , an aircraft 30 is shown which has a fuselage 32, two wings 34, arranged on either side of the fuselage 32, and propulsion units 36 fixed under the wings 34. Each propulsion unit 36 comprises a nacelle 38 and a turbomachine 40 positioned inside the nacelle 38.

[0024] According to an embodiment visible on the figure 3 , the turbomachine 40 comprises, at the rear, a primary ejection duct 42, through which burnt gases escape in the turbomachine 40, which is delimited on the outside by an outer wall 44 and on the inside by an inner wall 46 extended by a nozzle cone 48.

[0025] According to one configuration, the outer and inner walls 44, 46 each comprise at least one acoustic absorption structure 50.

[0026] Each acoustic absorption structure 50 comprises an outer surface SE in contact with a medium in which acoustic waves propagate and an inner surface SI opposite the outer surface SE.

[0027] Although described as applied to a primary ejection duct 42, the invention is not limited to this application. Thus, the acoustic absorption structure 50 can be positioned at walls which have an outer surface SE in contact with a medium in which sound waves propagate.

[0028] Each sound absorption structure 50 comprises at least one alveolar structure 52 interposed between an acoustically resistive layer 54 permeable to sound waves and a reflective layer 56 impermeable to sound waves. The acoustically resistive layer 54 has a first face 54.1 corresponding to the outer surface SE and a second face 54.2 oriented towards the alveolar structure 52 and connected to the latter. The reflective layer 56 has a first face 56.1 corresponding to the inner surface SI and a second face 56.2 oriented towards the alveolar structure 52 and connected to the latter.

[0029] The acoustically resistive layer 54, the reflective layer 56, the connection between the acoustically resistive layer 54 and the honeycomb structure 52 as well as the connection between the reflective layer 56 and the honeycomb structure 52 are not further described because they may be identical to those of the prior art.

[0030] The honeycomb structure 52 extends between a first face 52.1 in contact with the acoustically resistive layer 54 and a second face 52.2 in contact with the reflective layer 56 and comprises a multitude of substantially rectangular walls 58.1 to 58.6 which each have first and second edges positioned respectively at the level of the first and second faces 52.1, 52.2. These walls 58.1 to 58.6 are connected to each other so as to delimit cells 60 opening at the level of the first and second faces 52.1, 52.2.

[0031] According to one embodiment, the cellular structure 52 is a honeycomb structure. As illustrated in the figure 10 , each cell 60 is delimited by six walls 58.1 to 58.6 and has a hexagonal section with six identical sides of width L60. Each hexagonal cell 60 comprises an inscribed circle of cell diameter D60. The cell diameter D60 is between 9.6 and 19.1 mm. Each cell 60 has a cell height H60 (visible on the figure 14 ) which corresponds to the distance separating the first and second faces 52.1, 52.2. The cell height H60 is between 30 and 70 mm. Each rectangular wall 58.1 to 58.6 has a length equal to the cell height H60, between 30 and 70 mm, and a width between approximately 5 and 12 mm.

[0032] Of course, the invention is not limited to this embodiment for the cells 60. Each of them opens at the level of first and second ends closed respectively by the acoustically resistive layer 54 and the reflective layer 56. Each of them is delimited by planar walls 58.1 to 58.6 including two fixing walls 58.1, 58.2.

[0033] The honeycomb structure 52 comprises at least one partition tube 62 positioned in a cell 60. According to one configuration, the honeycomb structure 52 comprises several partition tubes 62 each positioned in a cell 60. According to one arrangement, in at least one area of the honeycomb structure 52, the latter comprises a partition tube 62 in each cell 60, as illustrated in the figures 4 And 5 .

[0034] As illustrated on the figures 8 And 10, each partition tube 62 comprises a first conduit 64 which extends between first and second ends 64.1, 64.2 and has a first section S1 between the first and second ends 64.1, 64.2, a second conduit 66 which extends between first and second ends 66.1, 66.2 and has a second section S2 between the first and second ends 66.1, 66.2, the second section S2 being smaller than the first section S1, as well as a junction wall 68 connecting the second ends 64.2, 66.2 of the first and second conduits 64, 66. According to one configuration, the second section S2 is 25% smaller than the first section S1, preferably 15% smaller.

[0035] Each partition tube 62 is produced in one piece, the first and second conduits 64, 66 as well as the junction wall 68 being produced during the same manufacturing step.

[0036] According to one embodiment, the first section S1 is constant over a first height H1, between the first and second ends 64.1, 64.2. Thus, the first conduit 64 has a first axis A64. The first height H1 is between 1 and 20 mm. According to one arrangement, the first height H1 is between 25% and 75% of the cell height H60. According to one configuration, the first height H1 is substantially equal to half the cell height H60.

[0037] According to one embodiment, the second section S2 is constant over a second height H2, between the first and second ends 66.1, 66.2. Thus, the second conduit 66 has a second axis A66. According to one embodiment, the second section S2 is circular. According to one configuration, the second section S2 is between 0.15 mm 2< and 20 mm 2< , which corresponds respectively to diameters of approximately 0.5 mm and 5 mm. The second height H2 is between 10 and 25 mm.

[0038] According to one arrangement, the first and second axes A64 and A66 are aligned.

[0039] According to one embodiment, the junction wall 68 is located in a plane perpendicular to the first axis A64, i.e. substantially perpendicular to the first conduit 64. Of course, the invention is not limited to this embodiment for the junction wall 68. The latter could not be flat and could be frustoconical for example.

[0040] According to a first embodiment visible on the figure 4 , the first end 64.1 of the first conduit 64 is positioned at the level of the first face 52.1 of the cellular structure 52 in order to be closed by the acoustically resistive layer 54 and connected to the latter in a sealed manner. The first end 66.1 of the second conduit 66 is spaced from the reflective layer 56 and from the second face 52.2 of the cellular structure 52 by a distance of between 0.5 mm and 70% of the cell height H60.

[0041] According to a second embodiment visible on the figure 5 , the first end 64.1 of the first conduit 64 is positioned at the level of the first face 52.2 of the cellular structure 52 in order to be closed by the reflective layer 56 and connected to the latter in a sealed manner. The first end 66.1 of the second conduit 66 is spaced from the acoustically resistive layer 54 and from the first face 52.1 of the cellular structure 52, by a distance of between 0.5 mm and 70% of the cell height H60.

[0042] Whatever the embodiment, the partition tube 62 divides the cell 60 in which it is positioned into first and second cavities 70.1, 70.2, the first cavity 70.1 being located inside the partition tube 62 and delimited by the partition tube 62 and a first layer among the resistive acoustic layer 54 and the reflective layer 56, the second cavity 70.2 being located outside the partition tube 62 and delimited by the walls 58.1 to 58.6 of the alveolar structure 52; the partition tube 62, the reflective layer 56 and the acoustically resistive layer 54, the first and second cavities 70.1, 70.2 communicating via the second conduit 66. Thus, one of the cavities 70.1, 70.2 forms a first Helmholtz type resonator suitable for attenuating low-frequency sound waves. In addition, the other cavity 70.1, 70.2 forms a second ¼-wave type resonator suitable for attenuating high-frequency sound waves.

[0043] This solution provides an acoustic absorption structure configured to attenuate sound waves over a wide frequency band or over several frequency bands.

[0044] According to the embodiment visible on the figure 4 , the first cavity 70.1 forms a first Helmholtz type resonator suitable for attenuating low-frequency sound waves. In addition, the second cavity 70.2 forms a second ¼-wave type resonator suitable for attenuating high-frequency sound waves.

[0045] According to a feature of the invention visible on the figures 12 à 16 , the first conduit 64 of the partition tube 62 comprises at least two flats 72, 72' pressed against at least first and second fixing walls 58.1, 58.2 adjacent among the walls 58.1 to 58.6 of the cell 60 and fixed to the latter as well as at least one side wall 74 distant from the other walls 58.3 to 58.6 of the cell 60, called distant walls.

[0046] Each flat 72, 72' is fixed to a fixing wall 58.1, 58.2 by any suitable means, such as gluing, welding, stapling or other means, depending on the nature of the elements to be assembled.

[0047] According to one configuration, each flat 72, 72' extends over the entire height of the first conduit 64, from the first end 64.1 to the second end 64.2.

[0048] According to one embodiment, each wall 58.1 to 58.6 of the cell 60 comprises a first end edge 58a located at the second face 52.2 of the cellular structure 52, a second end edge 58b located at the first face 52.1 of the cellular structure 52 as well as lateral edges 58c, 58d connecting the first and second end edges 58a, 58b. The first and second fixing walls 58.1, 58.2 are connected by a common lateral edge 58c.

[0049] The cell 60 having a hexagonal section, the fixing walls 58.1, 58.2 form an angle of 120° between them. In addition, the flats 72, 72' form an angle of the order of 120° between them so as to be pressed against the first and second fixing walls 58.1, 58.2. Each flat 72, 72' has a width less than that of the corresponding first or second fixing wall 58.1, 58.2.

[0050] Each side wall 74 is spaced from the distant walls 58.3 to 58.6 of the cell 60 by a substantially constant distance. According to one embodiment, the side wall 74 comprises two plane parts 74.1, 74.2 parallel to each other and connected to the flats 72, 72' as well as a curved part 74.3 connecting the two plane parts 74.1, 74.2.

[0051] According to one arrangement, the curved portion 74.3 of the side wall 74 is a cylindrical portion having an axis coincident with the first axis A64 of the first conduit 64.

[0052] Each flat 72, 72' forms an angle of the order of 120° with the flat part 74.1, 74.2 of the adjacent side wall 74.

[0053] The flat and curved portions 74.1, 74.2, 74.3 of the side wall 74 are spaced from the third, fourth, fifth and sixth distant walls 58.3 to 58.6 facing them by a distance of between 5% and 50% of the diameter D60 of the circle inscribed in the first section S1.

[0054] According to one configuration, the partition tube 62 comprises an intermediate zone 76, separating the two flats 72, 72', spaced from the lateral edge 58c common to the first and second fixing walls 58.1, 58.2. According to one arrangement, this intermediate zone 76 is flat and extends over the entire height of the first conduit 64, from the first end 64.1 to the second end 64.2. The intermediate zone 76 forms with each flat 72, 72' an angle of the order of 150° and has a width (dimension taken perpendicular to the first end 64.1) of the order of a few millimeters, less than half the width of a flat 72, 72'.

[0055] According to the invention, the partition tube 62 is connected to at least two fixing walls 58.1, 58.2 of the cell 60 in which the partition tube 62 is positioned, and at most four distant walls 58.3 to 58.6. Thus, the cell 60 comprises at least first and second adjacent fixing walls 58.1, 58.2 to which the partition tube 62 is connected as well as at least two distant walls 58.3 to 58.6 spaced from the partition tube 62. To the extent that the partition tube 62 is not connected to all the walls 58.1 to 58.6 of the cell 60, the honeycomb structure 52 retains a certain flexibility. Thus, the honeycomb structure 52 retains a flexibility allowing it to be shaped. The flexibility of the honeycomb structure 52 is all the more important as the number of walls to which the partition tube 62 is connected is low.

[0056] According to a first embodiment visible on the figure 6 , a method of manufacturing an acoustic absorption structure comprises a step of producing a honeycomb structure 52 comprising first and second planar faces 52.1, 52.2, a step of placing the acoustically resistive layer 54 on the first face 52.1 of the honeycomb structure 52 as illustrated in part (A) of the figure 6 , a step of inserting each partition tube 62 into a cell 60 as illustrated in part (B) of the figure 6 , a step of fixing the partition tube 62 inserted into the cell 60 to at least two fixing walls 58.1, 58.2 of the cell 60 as illustrated in part (C) of the figure 6 , a possible step of forming the honeycomb structure 52 as well as a step of placing the reflective layer 56 on the second face 52.2 of the honeycomb structure 52 as illustrated in part (D) of the figure 6 .

[0057] According to a second embodiment visible on the figure 7 , a method of manufacturing an acoustic absorption structure comprises a step of producing a honeycomb structure 52 comprising first and second planar faces 52.1, 52.2, a step of placing the reflective layer 56 on the second face 52.2 of the honeycomb structure 52 as illustrated in part (A) of the figure 7 , a step of inserting each partition tube 62 into a cell 60 as illustrated in part (B) of the figure 7 , a step of fixing the partition tube 62 inserted into the cell 60 to at least two fixing walls 58.1, 58.2 of the cell 60 as illustrated in part (C) of the figure 7 , a possible step of forming the honeycomb structure 52 as well as a step of placing the acoustically resistive layer 54 on the first face 52.1 of the honeycomb structure 52 as illustrated in part (D) of the figure 7 .

[0058] According to another embodiment, a method for manufacturing an acoustic absorption structure comprises a step of producing a honeycomb structure 52 comprising first and second planar faces 52.1, 52.2, a step of inserting each partition tube 62 into a cell 60, a step of fixing the partition tube 62 inserted into the cell 60 to at least two fixing walls 58.1, 58.2 of the cell 60, a step of forming the honeycomb structure 52 as well as steps of placing an acoustically resistive layer 54 and a reflective layer 56 carried out after the step of fixing the partition tubes 62 in the cells 60 of the honeycomb structure 52.

[0059] The step of inserting the partition tubes 62 can be done individually, partition tube after partition tube, or in groups, several partition tubes being inserted simultaneously.

[0060] The step of inserting the partition tubes 62 can be mechanized and / or carried out before or after the forming step.

[0061] According to one method of operation, during the step of fixing each partition tube 62, at least one centering element is used to keep the partition tube 62 spaced from the distant walls 58.3 to 58.6.

[0062] According to one embodiment, the honeycomb structure 52 may be metallic or made of composite material. The partition tubes 62 may be metallic, made of composite material or made of plastic.

[0063] When made of plastic, the partition tubes 62 can be produced by an extrusion blow molding, injection molding or stamping process for example.

[0064] According to one operating mode, the manufacturing method comprises a step of cutting at least one partition tube from a part 78.

[0065] So, as illustrated on the figure 11 , two partition tubes 62, 62' can be cut from the same part 78 made in one piece. This part 78 comprises a central section 80 which has a section identical to that of the first conduit 64 of each partition tube 62, 62' as well as two secondary sections 82, 82' positioned on either side of the central section 80 and extending it, each of the secondary sections 82, 82' having a section identical to that of the second conduit 66 of each partition tube 62, 62'. The central section 80 has a length L80 greater than the sum of the lengths of two first conduits 64. Thus, this central section 80 comprises two first conduits 64 of two partition tubes 62, 62' and an excess length 80.1. In addition, each secondary section 82, 82' has a length L82, L82' greater than that of the second conduit 66 of the partition tubes 62, 62'.Thus, each secondary section 82, 82' comprises a second conduit 66 of a partition tube 62, 62' and an excess length 82.1, 82.1'. According to this embodiment, from a single piece 78 made in one piece, it is possible to cut two partition tubes 62, 62', each of them having a first conduit 64 with a suitable length which may be different from one partition tube to the other. In addition, it is possible to cut the two secondary sections 82, 82' in order to adjust the length of the second conduit 66 of each of the partition tubes 62, 62'.

[0066] Of course, the invention is not limited to this method of production for repair tubes.

[0067] According to a characteristic of the invention visible on the figure 16 , the acoustic absorption structure 50 comprises at least a first drainage network 84 intersecting with the first cavity 70.1 located inside the partition tube 62 positioned in a given cell 60 as well as at least a second drainage network 86 intersecting with the second cavity 70.2 located outside the partition tube 62, between the partition tube 62 and the cell 60.

[0068] The first drainage network 84 comprises at a cell 60 first and second openings 84.1, 84.2 passing through the first and second fixing walls 58.1, 58.2. In addition, the second drainage network 86 comprises at the cell 60 third and fourth openings 86.1, 86.2 passing through third and fourth walls 58.3, 54.4 opposite the first and second fixing walls 58.1, 58.4. The first, second, third and fourth openings 84.1, 84.2, 86.1, 86.2 are located at the first or second end edges 58a, 58b of the walls 58.1 to 58.6 at which the first end 64.1 of the first conduit 64 of the partition tube 62 is positioned.

[0069] To ensure continuity between the first and second openings 84.1, 84.2, the partition tube 62 comprises at least one notch 88 which extends from the first end 64.1 of the first conduit 64, said notch 88 being configured to clear at least the first and second openings 84.1, 84.2 when the partition tube 62 is fixed to the first and second fixing walls 58.1, 58.2. According to a first configuration, the partition tube 62 comprises two notches, one for each of the first and second openings 84.1, 84.2. According to a second configuration visible on the figures 9 And 12 à 16, the partition tube 62 comprises a single notch 88 which clears the first and second openings 84.1, 84.2 and extends over the two flats 72, 72' and the intermediate zone 76. This notch 88 is delimited by a first edge 88.1 substantially parallel to the first end 64.1 of the first conduit 64 as well as second and third edges 88.2, 88.3, substantially perpendicular to the upper end 64.1, connecting the first end 64.1 and the first edge 88.1, close to the two flat parts 74.1, 74.2 of the side wall 74 and distant from the side wall 74. The notch 88 is distant from the side wall 74, in particular from the two flat parts 74.1, 74.2 of the side wall 74. Thus, the flats 72, 72' each comprise a strip of material 72.1 which extends to the first end 64.1 of the first conduit 64 so that the two strips of material 72.1 of the flats 72, 72' are pressed and fixed against the first and second fixing walls 58.1, 58.2 up to the first end 64.1 on either side of the notch 88.

[0070] The fact that the partition tube 62 is connected to first and second fixing walls 58.1, 58.2 and comprises at least one notch 88 clearing the first and second openings 84.1, 84.2 provided at the level of the first and second fixing walls 58.1, 58.2 makes it possible to isolate the first drainage network 84 from the second drainage network 86.

[0071] According to one embodiment, in a given area, each cell 60 of the cellular structure 52 comprises a partition tube 62. The first and second fixing walls 58.1, 58.2 are connected to each other so as to form, in top view, at least one first broken line 90. In parallel, the third and fourth walls 58.3, 58.4 are connected to each other so as to form, in top view, at least one second broken line 92 spaced from the first broken line 90 and connected to the latter by fifth and sixth walls 58.5, 58.6 parallel to each other and not notched.

[0072] The partition tubes 62 are positioned on either side of the first broken line 90 and connected to the first and second fixing walls 58.1, 58.2. Thus, each of the first and second fixing walls 58.1, 58.2 is connected to two partition tubes 62 positioned on either side of the fixing wall 58.1, 58.2.

[0073] According to this embodiment, the cellular structure 52 comprises several first drainage networks 84, each of them being positioned on either side of a first broken line 90 and comprising the first and second openings 84.1, 84.2 provided at the first and second fixing walls 58.1, 58.2 which form the first broken line 90 as well as the first cavities 70.1 of the partition tubes 62 connected to the first and second fixing walls 58.1, 58.2 which form the first broken line 90. In addition, the cellular structure 52 comprises several second drainage networks 86, each of them being positioned on either side of a second broken line 92 and comprising the third and fourth openings 86.1, 86.2 provided at the third and fourth walls 58.3, 58.4 which form the second line broken 92 as well as the second cavities 70.2 of the cells 60 positioned on either side of the second broken line 92.

[0074] According to one operating mode, the method for manufacturing an acoustic alveolar structure 52 comprises at least one grooving step to produce the openings 84.1, 84.2, 86.1, 86.2 of the first and second drainage networks 84, 86. This grooving step is carried out before the steps of inserting the partition tubes 62 and the steps of placing the acoustically resistive layer 54 and the reflective layer 56.

[0075] Of course, the invention is not limited to these embodiments for the first and second drainage networks 84, 86.

Claims

1. Sound absorption structure comprising at least one alveolar structure (52) interposed between an acoustically resistive layer (54) and a reflective layer (56), the alveolar structure (52) comprising a first face (52.1) in contact with the acoustically resistive layer (54), a second face (52.2) in contact with the reflective layer (56) as well as a multitude of cells (60) each opening at the first and second faces (52.1, 52.2), each cell (60) being delimited by walls (58.1 to 58.6); characterized in thatthe honeycomb structure (52) comprises at least one partition tube (62), positioned in one of the cells (60), comprising a first duct (64) which extends between first and second ends (64.1, 64.2) and has a first section (S1) between the first and second ends (64.1, 64.2), a second duct (66) which extends between first and second ends (66.1, 66.2) and has a second section (S2) between the first and second ends (66.1, 66.2), the second section (S2) being smaller than the first section (S1), as well as a junction wall (68) connecting the second ends (64.2, 66.2) of the first and second ducts (64, 66), the first end (64.1) of the first duct (64) being closed by a first layer among the acoustically resistive layer (54) and the layer reflector (56), the first end (66.1) of the second conduit (66) being spaced apart by a second layer, different from the first layer, among the acoustically resistive layer (54) and the reflective layer (56), the first conduit (64) of the partition tube (66) comprising at least two flats (72, 72') and at least one side wall (74), the walls (58.1 to 56.6) which delimit the cell (60) in which the partition tube (62) is inserted comprising at least first and second flat fixing walls (58.1, 58.2) against which the flats (72, 72') of the partition tube (62) are pressed and fixed as well as at least two distant walls (58.3 to 58.6) spaced apart from the side wall (74) of the partition tube (62).

2. Sound absorption structure according to claim 1, characterized in thatthe sound-absorbing structure comprises at least one first drainage network (84) which has first and second openings (84.1, 84.2) passing through the first and second fixing walls (58.1, 58.2) as well as at least one second drainage network (86) which has third and fourth openings (86.1, 86.2) passing through third and fourth walls (58.3, 54.4) opposite the first and second fixing walls (58.1, 58.4).

3. Sound absorption structure according to the preceding claim, characterized in that each wall (58.1 to 58.6) of the cell (60) in which the partition tube (62) is positioned comprises first and second end edges (58a, 58b) located at the first and second faces (52.1, 52.2) of the honeycomb structure (52) and in thatthe first, second, third and fourth openings (84.1, 84.2, 86.1, 86.2) are located at the first or second end edges (58a, 58b) of the walls (58.1 to 58.6) at which the first end (64.1) of the first conduit (64) of the partition tube (62) is positioned.

4. Sound absorption structure according to the preceding claim, characterized in that the partition tube (62) comprises at least one notch (88) which extends from the first end (64.1) of the first conduit (64), said notch (88) being configured to clear at least the first and second openings (84.1, 84.2) when the partition tube (62) is fixed to the first and second fixing walls (58.1, 58.2).

5. Sound absorption structure according to the preceding claim, characterized in that the partition tube (62) comprises a single notch (88) which clears the first and second openings (84.1, 84.2).

6. Sound absorption structure according to the preceding claim, characterized in that the notch (88) is delimited by a first edge (88.1) as well as second and third edges (88.2, 88.3), connecting the first edge (88.1) and the upper end (64.1) of the first conduit (64), distant from the side wall (74).

7. Sound absorption structure according to one of the preceding claims, characterized in that the first and second fixing walls (58.1, 58.2) are connected by a common lateral edge (58c) and in that the partition tube (62) comprises an intermediate zone (76), separating the two flats (72, 72'), spaced from the lateral edge (58c) common to the first and second fixing walls (58.1, 58.2).

8. Sound absorption structure according to one of the preceding claims, characterized in that each flat (72, 72') extends from the first end (64.1) to the second end (64.2) of the first conduit (64).

9. Sound absorption structure according to one of the claims, characterized in that the side wall (74) comprises two flat parts (74.1, 74.2) parallel to each other and connected to the flats (72, 72') as well as a curved part (74.3) connecting the two flat parts (74.1, 74.2), the flat and curved parts (74.1, 74.2, 74.3) of the side wall (74) being spaced from the walls (58.3 to 58.6) of the cell (60) in which the partition tube (62) is positioned.

10. Sound absorption structure according to one of the preceding claims, characterized in that, on a given area, each cell (60) of the honeycomb structure (52) comprises a partition tube (62) connected to first and second fixing walls (58.1, 58.2) crossed by first and second openings (84.1, 84.2) and spaced from third and fourth walls (58.3, 58.4) opposite the first and second fixing walls (58.1, 58.2) and crossed by third and fourth openings (86.1, 86.2), in that the first and second fixing walls (58.1, 58.2) of the cells (60) are connected to each other so as to form, in top view, at least one first broken line (90), the partition tubes (62) being positioned on either side of the first broken line (90) and connected to the first and second fixing walls (58.1, 58.2), and in thatthe third and fourth walls (58.3, 58.4) of the cells (60) are connected to each other so as to form, in top view, at least a second broken line (92) spaced from the first broken line (90). 1

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