Acoustic attenuation device

Abstract

The invention relates to an acoustic attenuation device comprising at least one air flow conduit intended to channel an air flow in an air flow direction in the conduit, the acoustic attenuation device comprising at least one acoustic attenuation member, in particular a Helmholtz resonator, comprising a cavity and a neck connecting the cavity to the conduit, the neck having a cross-section with a width measured in the air flow direction in the air flow conduit and a length measured in a direction perpendicular to that of the width, the length being strictly greater than the width.

Description

SOUND ATTENUATION DEVICE [1] The subject of the invention is a sound attenuation device configured to be mounted in a ventilation, heating and / or air conditioning installation of a motor vehicle which comprises such a sound attenuation device or in a front panel module of a motor vehicle which comprises the sound attenuation device, as well as a ventilation, heating and / or air conditioning installation of a motor vehicle which comprises such a sound attenuation device and a front panel module of a motor vehicle which comprises the sound attenuation device. [2] Generally, a motor vehicle comprises an air inlet in the form of an opening located on the front face of said motor vehicle. The incoming air is used to enable heat exchange between it and the cooling system of the motor vehicle, said cooling system being located near the front face of said vehicle. More specifically, the air entering the engine compartment of the motor vehicle is guided by ducts towards the cooling system of said motor vehicle to enable heat exchange between the incoming air and the heat exchanger of the cooling system. It is important to minimize losses of air flow between the air inlet and the heat exchanger.Indeed, any air flow entering the interior of the vehicle, and escaping towards the engine compartment before having contributed to the heat exchange inside the motor vehicle, negatively influences the air resistance coefficient of said motor vehicle. It is known to use an air flow duct to channel the circulating air flow. [3] Ventilation, heating and / or air conditioning systems fitted to motor vehicles allow users of the motor vehicle to control a supply of cold air and / or hot air to different areas of the passenger compartment, such as at the driver's footwell, on a glass surface of the vehicle and / or at passenger level. It is known to use an air flow duct to channel the circulating air flow. Such a duct ensures the flow and distribution of an air flow. In these ducts, noise pollution is generated. Indeed, the acoustic waves generated by the motor-fan unit propagate along the air duct and radiate towards the front of the vehicle. In addition, the circulation of air through such ventilation, heating and / or air conditioning systems promotes the emission of numerous acoustic waves when these systems force the circulation of air towards the passenger compartment, for example. The acoustic waves produced can cause discomfort to the driver and / or passengers. [4] A front panel module allows heat exchange and battery cooling in the case of an electric vehicle. Here too, it is known to use an airflow flow duct to channel the airflow circulating in the front panel module. Such a duct ensures the flow and distribution of an airflow. In these ducts, noise pollution is generated. To overcome this, it is known to equip these airflow flow ducts with at least one acoustic attenuation member to reduce the noise emitted by the air circulating in the ducts, in particular when charging an electric vehicle. To allow a reduction in acoustic waves, this type of acoustic attenuation member comprises a Helmholtz resonator to reduce the acoustic energy radiated on the front of the vehicle at a given frequency. [5] A Helmholtz resonator comprises, in a known manner, a cavity and a neck, generally cylindrical in shape and circular in cross-section, connecting the cavity to an airflow duct. The interaction between the airflow and the neck of the resonator can cause acoustic disturbances and regenerate secondary noises which degrade the performance of the acoustic attenuation device comprising resonators. These generated noises can be tonal whistling or broadband noises. These noises are caused by pressure fluctuations linked to interactions of the airflow and the neck of the resonators which modify the impedance of the latter and therefore modify these performances. The resonator then loses efficiency, or even generates noise. [6] In this context, the present invention provides an acoustic attenuation device in which the generation of acoustic waves linked to the interaction between the air flow and acoustic attenuation members arranged in the duct are reduced or avoided. [7] The invention relates to an acoustic attenuation device comprising at least one air flow duct intended to channel an air flow along a direction of air flow in the duct, the acoustic attenuation device comprising at least one acoustic attenuation member, in particular a Helmholtz resonator, comprising a cavity and a neck connecting the cavity to the duct, the neck having a section having a width measured in the direction of air flow in the air flow duct and a length measured in a direction perpendicular to that of the width, the length being strictly greater than the width. [8] Thus, the device according to the invention makes it possible to reduce the interaction of the air flow with the acoustic attenuation member and thus to reduce or avoid the regeneration of noise generating an acoustic disturbance such as broadband noise. [9] According to one aspect of the invention, the device comprises a network of acoustic attenuation members arranged on at least one wall of the air flow duct, the acoustic attenuation members of the network being distributed at least parallel to the direction of air flow.

[0010] According to one aspect of the invention, the network of acoustic attenuation members comprises a first row of substantially similar acoustic attenuation members extending along a first direction perpendicular to the airflow direction, the network of acoustic attenuation members comprising at least a second row of substantially similar acoustic attenuation members extending along a second direction perpendicular to the first direction and to the airflow direction.

[0011] According to one aspect of the invention, the network of acoustic attenuation members is organized in the form of a matrix comprising at least two rows of acoustic attenuation members, and where the acoustic attenuation members of the at least two rows are respectively aligned along the air flow direction. It is understood that each acoustic attenuation member of one of the two rows of acoustic attenuation members is aligned with at least one acoustic attenuation member of the other of the two rows of acoustic attenuation members, along a direction perpendicular to the air flow direction.

[0012] According to one aspect of the invention, the neck of the acoustic attenuation member opens into the air flow duct, forming an opening in said duct.

[0013] According to one aspect of the invention, the neck has a rectangular section or an oval section, said section having a width measured in the direction of air flow in the air flow duct and a length measured in a direction perpendicular to that of the width, the length being strictly greater than the length.

[0014] According to one aspect of the invention, the neck has a height measured along a main extension axis of the neck, the height of the neck being between one millimeter and twenty-five millimeters.

[0015] According to one aspect of the invention, the cavity of an acoustic attenuation member comprises at least four faces delimiting a volume.

[0016] According to one aspect of the invention, at least one cavity of the network of acoustic attenuation members has a parallelepiped shape.

[0017] According to one aspect of the invention, the cavity of the acoustic attenuation member has a rectangular section

[0018] According to one aspect of the invention, the network of acoustic attenuation members extends over at least two, preferably at least three, preferably at least four walls forming the air flow duct.

[0019] According to one aspect of the invention, the neck has a section having a width measured in the direction of air flow in the airflow duct and a length measured in a direction perpendicular to that of the width, the length being 2 times greater, preferably 5 times greater, preferably 10 times greater, preferably 15 times greater, preferably 20 times greater, preferably more than 20 times greater than the width.

[0020] In other words, the ratio of neck length to neck width is greater than 1, preferably greater than 2, preferably greater than 5, preferably greater than 10, preferably greater than 15, preferably greater than 20.

[0021] According to one aspect of the invention, the neck opens onto the airflow flow duct by forming a slot comprising a downstream edge and an upstream edge, the upstream edge being presented first in the airflow flow direction and the downstream edge being placed behind the upstream edge in the airflow flow direction.

[0022] According to one aspect of the invention, the neck has a downstream section adjacent to the slot which extends towards the downstream edge of the slot in a flared manner by divergence towards the slot.

[0023] In this way, the air flow having first interacted with the upstream edge slides over the flared downstream section before entering the cavity instead of hitting the downstream edge and therefore generating noise pollution.

[0024] According to one aspect of the invention, the height of the flared downstream section is less than 50% of the total height of the neck, preferably less than 40% of the height of the neck, preferably less than 30% of the total height of the neck, preferably less than 20% of the total height of the neck.

[0025] According to one aspect of the invention, the flared downstream section is chamfered.

[0026] According to one aspect of the invention, the flared downstream section has an inclination of an angle of between 20° and 60°, in particular between 30° and 50°, in particular of approximately 45°, relative to the main extension axis of the neck.

[0027] By principal axis of extension of the neck is meant here an axis which extends in the direction of the height of the neck.

[0028] According to one aspect of the invention, the neck has an upstream section adjacent to the slot which extends straight towards the upstream edge of the slot.

[0029] According to one aspect of the invention, the upstream section is substantially parallel to the main axis of the pass.

[0030] The present invention also relates to a ventilation, heating and / or air conditioning installation for a motor vehicle which comprises an acoustic attenuation device as described in the present document, the acoustic attenuation device being installed at an air outlet or inlet of the ventilation, heating and / or air conditioning installation.

[0031] The present invention also relates to a front panel module of a motor vehicle which comprises an acoustic attenuation device as described in the present document, the acoustic attenuation device being installed at an air inlet on the front panel of the motor vehicle.

[0032] Other characteristics and advantages of the present invention will appear more clearly on reading the following description, provided for illustrative and non-limiting purposes, and the appended drawings in which:

[0033] [Fig 1] Figure 1 is a schematic representation of a ventilation, heating and / or air conditioning installation of a motor vehicle according to the invention;

[0034] [Fig 2] Figure 2 is a schematic representation of a front end module of a motor vehicle according to the invention;

[0035] [Fig 3] Figure 3 is a schematic representation of an acoustic attenuation device according to the invention;

[0036] [Fig 4] Figure 4 is a schematic representation of an acoustic attenuation member of an acoustic attenuation device according to the invention;

[0037] [Fig 5] Figure 5 is a schematic representation of a part of a network of acoustic attenuation members of a device according to the invention;

[0038] [Fig 6] Figure 6 is a schematic representation of the neck of an acoustic attenuation member of an acoustic attenuation device according to the invention;

[0039] [Fig 7] Figure 7 is a schematic cross-sectional representation of the neck of an acoustic attenuation member of an acoustic attenuation device according to a first variant.

[0040] Figure 1 is a schematic representation of a ventilation, heating and / or air conditioning installation of a motor vehicle according to the invention. The ventilation, heating and / or air conditioning installation of a motor vehicle 1 here comprises a fan 3 which generates the formation of an air flow F but also of an acoustic wave A. Several acoustic attenuation devices 4 comprising acoustic attenuation members 8, or networks of acoustic attenuation members 8bis are arranged on the ventilation, heating and / or air conditioning installation 1. Alternatively, there could be a single acoustic attenuation device 4 in the installation 1. The acoustic attenuation device 4 comprises a duct 2 for the flow of an air flow F and in which the acoustic wave A propagates. The air flow enters through an air inlet not shown here by being sucked in by the fan 3 and then is directed by said fan 3 towards an air outlet. The acoustic waves A circulate here in the opposite direction to the air flow sucked in by the fan 3 and in the same direction as the air flow which is directed towards an air outlet.The acoustic attenuation members of each acoustic attenuation device are arranged on the walls 13 of the duct 2 for the flow of the air flow F.

[0041] Figure 2 is a schematic representation of a front end module of a motor vehicle, and more precisely of a front end module 100 comprising an air inlet 101 through which an air flow F enters, at least one heat exchanger 102 and a fan 103 arranged to suck in the air flow F entering through the air inlet 101 and direct said air flow F towards an air outlet. The front panel module 100 here comprises at least one acoustic attenuation device 4 arranged on the air inlet 101. The acoustic attenuation device comprises a duct 2 arranged for the passage of the air flow F and the propagation of an acoustic wave A. Here, the acoustic wave A moves in the opposite direction to the air flow F in the air flow flow duct 2. The acoustic attenuation device here comprises several acoustic attenuation members 8. The acoustic attenuation device is arranged on the walls 13 of the air flow flow duct 2 F.

[0042] Figure 3 is a schematic representation of an acoustic attenuation device 4. In this figure, the acoustic attenuation device 4 comprises an array 8bis of acoustic attenuation members 8. On this array 8bis, the acoustic attenuation members 8 are arranged in several rows and are parallel in the same row and from one row to another. The device 1 comprises a duct 2 for the flow of an air flow F in which an acoustic wave can propagate. The acoustic attenuation members are arranged on the walls 13 of the air flow duct 2. The acoustic attenuation members are here Helmholtz resonators.The acoustic attenuation members 8 comprise a cavity 6 and a neck 7 connecting the cavity 6 to the duct 2, the neck 7 having a section 14 having a width I measured in the direction of flow of the air flow F in the duct 2 of flow of the air flow and a length L measured in a direction perpendicular to that of the. width I, the length L being strictly greater than the width I. The neck 7 of the acoustic attenuation members opens into the duct 2 for the flow of the air flow F, forming an opening 9 in said duct 2. Such a device makes it possible to reduce the interaction of the air flow F with the acoustic attenuation member 8 and thus to reduce or avoid the regeneration of noise generating an acoustic disturbance such as broadband noise. In this example, the cavities 6 of the acoustic attenuation members 8 may have different volumes. In a well-known manner, the cavities of the acoustic attenuation members have a rectangular section 14.

[0043] Figure 4 shows a sectional view of a network 8bis of acoustic attenuation members 8 of a device according to the invention. Each acoustic attenuation member 8 comprises a cavity 6 and a neck 7 connecting the cavity 6 to a wall 13 of the flow duct of the device. The neck 7 opens onto the flow duct 2 of the air flow F by forming a slot comprising a downstream edge 11 and an upstream edge 10, the upstream edge 10 occurring first in the direction of flow of the air flow F and the downstream edge 11 being placed behind the upstream edge 10 in the direction of flow of the air flow F. A downstream section 12 is present on each downstream edge 11.

[0044] Figure 5 is a representation of an acoustic attenuation member 8 of a device according to the invention. The acoustic attenuation member 8 comprises a cavity 6 and a neck 7 connecting the cavity 6 to a wall 13 of the flow duct of the device. The neck has a height h measured along a main extension axis of the neck, the height of the neck being between one millimeter and twenty-five millimeters. The neck 7 here has a rectangular section 14, said section 14 having a width I measured in the direction of flow of the air F in the flow duct 2 of the air flow F and a length L measured in a direction perpendicular to that of the width I, the length L being strictly greater than the width I.More precisely, the length L may be 2 times greater, preferably 5 times greater, preferably 10 times greater, preferably 15 times greater, preferably 20 times greater, preferably more than 20 times greater than the width I. In other words, the ratio of length L of the neck to width I of the neck is greater than 1, preferably greater than 2, preferably greater than 5, preferably greater than 10, preferably greater than 15, preferably greater than 20.

[0045] As can be seen in more detail in Figure 6, the neck 7 opens onto the duct 2 for the flow of the air flow F by forming a slot comprising a downstream edge 11 and an upstream edge 10, the upstream edge 10 appearing first in the direction of flow of the air flow F and the downstream edge 11 being placed behind the upstream edge 10 in the direction of flow of the air flow F. The neck 7 has a downstream section 12 adjacent to the slot which extends towards the downstream edge 11 of the slot in a flared manner by divergence in the direction of the slot. In this way, the air flow having first interacted with the upstream edge 10 slides on the flared downstream section 12 before entering the cavity 6 instead of hitting the downstream edge 11 and therefore generating a noise nuisance. The flared downstream section 12 is chamfered. The flared section 12 has an inclination relative to the main axis X of the neck which extends over the entire length of the neck 7. The flared section 12 has an angle alpha of between 20° and 60°, preferably an angle of 45° relative to said main extension axis X of the neck 7.

[0046] Figure 7 is a cross-sectional representation of the neck 7 of an acoustic attenuation member according to the invention. In Figure 7, the height of the flared downstream section is less than 30% of the total height of the neck, preferably less than 20% of the total height of the neck. In other words, the ratio of the height of the downstream section 12 to the total height of the neck h is less than 0.3.

Claims

CLAIMS

1. An acoustic attenuation device (4) comprising at least one flow duct (2) for an air flow (F) intended to channel an air flow (F) along a direction of air flow in the duct, the acoustic attenuation device (4) comprising at least one acoustic attenuation member (8), in particular a Helmholtz resonator, comprising a cavity (6) and a neck (7) connecting the cavity (6) to the duct (2), the neck (7) having a section (14) having a width (I) measured in the direction of flow of the air flow (F) in the flow duct (2) of the air flow and a length (L) measured in a direction perpendicular to that of the width (I), the length (L) being strictly greater than the width (I).

2. Acoustic attenuation device (4) according to claim 1, characterized in that it comprises a network (8bis) of acoustic attenuation members (8) arranged on at least one wall (13) of the duct (2) for the flow of the air flow (F), the acoustic attenuation members (8) of the network (8bis) being distributed at least parallel to the direction of flow of the air (F).

3. Acoustic attenuation device (4) according to one of the preceding claims, characterized in that the neck (7) has a section (14) having a width (I) measured in the direction of air flow in the air flow duct (2) and a length (L) measured in a direction perpendicular to that of the width (I), the length (L) being 2 times greater, preferably 5 times greater, preferably 10 times greater, preferably 15 times greater, preferably 20 times greater, preferably more than 20 times greater than the width (I).

4. Acoustic attenuation device (4) according to one of the preceding claims, characterized in that the neck (7) opens onto the flow duct (2) of the air flow (F) by forming a slot (15) comprising a downstream edge (11) and an upstream edge (10), the upstream edge (10) appearing first in the flow direction of the air flow (F) and the downstream edge (11) being placed behind the upstream edge (10) in the flow direction of the air flow (F).

5. Acoustic attenuation device (4) according to the preceding claim, characterized in that the neck (7) has a downstream section (12) adjacent to the slot (15) which extends in the direction of the downstream edge (11) of the slot (15) in a flared manner by divergence in the direction of the slot (15).

6. Acoustic attenuation device (4) according to the preceding claim, characterized in that the flared downstream section (12) is chamfered.

7. Acoustic attenuation device (4) according to the preceding claim, characterized in that the flared downstream section (12) has an inclination of an angle between 20° and 60° relative to a main extension axis (X) of the neck (7).

8. Acoustic attenuation device (4) according to one of claims 4 to 7, characterized in that the neck (7) has an upstream section (16) adjacent to the slot (15) which extends in the direction of the upstream edge (10) of the slot (15) in a straight manner.

9. Ventilation, heating and / or air conditioning installation of a motor vehicle (1) comprising an acoustic attenuation device (4) according to one of the preceding claims, the acoustic attenuation device (4) being installed at an air outlet or an air inlet of the ventilation, heating and / or air conditioning installation.

10. Front panel module (100) of a motor vehicle comprising an acoustic attenuation device (4) according to one of claims 1 to 8, the acoustic attenuation device (4) being installed at an air inlet (101) on the front panel of the motor vehicle.

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