FR2812442A1 - DEVICE FOR ACTIVE ATTENUATION OF SOUND WAVES PRODUCED BY AN EXHAUST LINE - Google Patents

Abstract

The invention concerns a device for active attenuation of sound waves produced by an exhaust line comprising a chamber (10) for exhaust gas circulation, a loudspeaker (12) and means for securing the loudspeaker (12) on the chamber (10). The chamber (10) comprises a wall (34) provided with an opening (36) bordered at its periphery with a support surface (40) for the loudspeaker (12). The securing means comprise a casing (14) provided with at least a support surface (54, 64) on the loudspeaker (12) and means (16) for stressing the casing (14) towards the chamber (10), the loudspeaker (12) being maintained enclosed between the chamber (10) and the casing (14). The invention is applicable to a motor vehicle exhaust line.

Description

The present invention relates to a device for active attenuation of

  sound waves produced by an exhaust line, of the type comprising an enclosure for the circulation of exhaust gases, a loudspeaker and

  means for securing the loudspeaker to the enclosure.

  Nowadays, it is known, in motor vehicles whose propulsion is provided by a heat engine, to provide, on the line

  exhaust, an active attenuation device for sound waves.

  Such a device comprises a loudspeaker mounted in an enclosure in which the exhaust gases circulate. The loudspeaker is connected to an electronic control circuit, the latter being connected to a noise sensor located on the exhaust line. The circuit is suitable for

  control the loudspeaker so that it generates noise canceling

  substantially reduce the noise produced by the exhaust line.

  For fixing the loudspeaker to the enclosure in which the exhaust gases circulate, it is known to provide, in the enclosure, a wall

  transverse provided with an opening in which the top is engaged

  speaker. The loudspeaker is held against the wall by screws passing through the

  speaker end crown at the periphery of its diaphragm

  bile. Due to the aggressive environment resulting from the circulation of exhaust gases, the loudspeaker degrades quickly. So it is often

  replacement of the speaker, without the need to replace

  place the speaker in which the speaker is installed. To replace the loudspeaker, it is first necessary to reach the loudspeaker by dismantling certain parts of the enclosure, then to dismantle the loudspeaker by removing

the connecting screws.

  Access to the loudspeaker is generally very difficult and requires disassembling many parts of the enclosure, which is awkward and time consuming,

  especially since the enclosure is not designed to be dismantled.

  The object of the invention is to propose an active attenuation device

  sound waves in which the speaker can be replaced easy-

  is lying. To this end, the invention relates to an active attenuation device for the sound waves produced by an exhaust line, of the aforementioned type, characterized in that the enclosure has a wall provided with an opening bordered at its periphery a bearing surface for the speaker, and in that the securing means comprise a box provided with at least one bearing surface on the speaker and means for urging the

  box towards the enclosure, the loudspeaker being held sandwiched between the

girdle and the box.

  According to particular embodiments, the device comprises one or more of the following characteristics: - the box has a first wall provided with a passage for the loudspeaker, and the loudspeaker is received at least partially inside the box; - The first wall has a bearing surface on the speaker defined at the periphery of the passage; - The box has a second wall extending opposite the first wall in the region of the passage delimited in the first wall, which second wall has a bearing surface on the speaker;

  - the or each bearing surface on the loudspeaker and the each over-

  corresponding face of the loudspeaker have complementary profiles ensuring an essentially tight coupling between the loudspeaker and the or each wall of the box; - The box has at least one bearing surface on the enclosure; - The box has a single bearing surface on the enclosure; - It includes a passage for connecting the interior spaces of the box and the enclosure; and

  the means for urging the box towards said enclosure comprising

  try toggle clamping mechanisms.

  The invention will be better understood on reading the description which will

  follow, given only as an example and made with reference to the

sins, on which:

  - Figure 1 is a perspective view of the attenuation device ac-

  sound waves according to the invention; and

  - Figure 2 is a longitudinal sectional view of the device of the

gure 1.

  The device shown in FIG. 1 is intended to be installed on an exhaust line of a motor vehicle with an internal combustion engine. This device constitutes the outlet section of the exhaust line. It essentially comprises an enclosure 10 for the circulation of gases

  exhaust, a loudspeaker 12 for producing an anti-noise and a case

  sound 14 biased towards enclosure 10 by biasing means 16, the loudspeaker

  loudspeaker 12 being held sandwiched between enclosure 10 and box 14. Loudspeaker 12 is connected to an excitation circuit allowing the loudspeaker

to produce noise canceling.

  The enclosure 10 has an envelope 20, generally cylindrical, closed at each of its ends by walls 22 and 23. A tube 24 passes right through the enclosure 10. 11 penetrates therein through the

  end wall 22 and protrudes through the opposite end wall 23.

  Inside the tube 24, in the region where the tube passes through the end wall 22, is arranged a member 26 promoting a laminar flow of the exhaust gases. This member 26 is formed, for example, by a honeycomb structure, the flat surfaces of which extend parallel to the axis of the tube. The exhaust gases circulate in the tube of the wall 22

towards the wall 23.

  Outside the enclosure 10, the tube 24 is surrounded, beyond the wall.

  end king 23, by a cannula 28 defining the outlet end of the

exhaust line.

  The interior of the cannula 28 communicates with the interior of the enclosure 10. The section of tube 24 surrounded by the cannula 28 is provided with slots 30,

  allowing the space delimited by the cannula to form a

  attenuation of sound waves by superimposing the noise of the exhaust line

  the noise generated by the loudspeaker 12.

  A noise sensor 32 is stitched onto the cannula 28. It is connected to the circuit

speaker excitement.

  The enclosure 10 has a substantially planar main face 34 on which the box 14 is attached. An opening 36 is delimited on

  this face opposite the speaker 12.

  A second opening 38 is provided on the face 34. This second opening 38 allows the interior space of

  the enclosure 10 and the interior space of the box 14.

  At the periphery of the opening 36, a surface 40 is defined which allows

  both the support of the crown formed by the enlarged end of the bowl

speaker.

  As known per se, the loudspeaker 14 comprises an external bowl

  laughter 42 locally openwork having an annular front face 44 main-

  naked against the bearing surface 40. Inside the bowl is arranged a rigid membrane 46 deformable in piston under the control of a set

  electromagnetic 48 comprising a coil connected to the excitation circuit.

  The box 14 has a generally parallelepiped shape. he

  comprises a first wall 50 extending opposite the face 34 of the

  belt 10. Parallel to this first wall 50 extends a second

  wall 52, generally parallel.

  The first wall 50 has a passage 54 for the loudspeaker

  12. Thus, the loudspeaker 12, and in particular its salad bowl 44 is essential-

  received inside the box 14. The passage 54 is bordered, at its periphery

  laughs, by an annular surface 56 intended to bear on the salad bowl 42 of the

  loudspeaker, in order to keep the loudspeaker pressed against the main face

blade 34 of the enclosure.

  For this purpose, the loudspeaker bowl, of generally truncated form

  conical, has an annular flat surface 58 forming a comfortable bearing surface

  adapted to cooperate with the bearing surface 56. The surfaces 56 and 58 have complementary profiles, so that when these surfaces

  are in contact, they define an essentially sealed junction.

  Opposite the passage 54, the second wall 52 of the box has a region 60 deformed towards the inside of the box 14. In this region, the

  wall 52 has a passage 62 for the rear part of the loudspeaker 12.

  This passage defines at its periphery a bearing surface 64 for the salad bowl

  42 from the speaker. This bearing surface is adapted to stress the built-in

  speaker towards the surface 34 of the enclosure. For this purpose, the bowl of the top-

  speaker has a second annular flat 66 adapted to cooperate with the bearing surface 62. These two surfaces define between them an essentially sealed junction, their profiles being complementary. The generally frustoconical section of the speaker bowl,

  defined between the two flats 58 and 66 is provided with openings, thus allowing

  if a connection between the membrane 46 and the interior of the box

  sound 14. On the other hand, the front and rear ends of the general bowl-

  frustoconical speaker, defined on either side of flats 58,

  66 are formed by solid surfaces.

  Furthermore, the wall 50 of the box has an external bending 70 in its region located opposite the passage 38. This bending 70 is provided with an opening 72 aligned with the opening 38 formed in the wall of the enclosure 10. The periphery of the opening 72 forms an annular surface 74 for supporting the box 14 on the face 34 of the enclosure 10. This support surface

  is the only direct bearing surface of the box 14 on the enclosure 10.

  Advantageously, and as illustrated in the figures, the means 16 for urging the box 14 against the main face 34 of the silencer 10 are formed by four latches mechanisms distributed around the periphery of

  the enclosure and the box. These mechanisms include hooks 80 articulated

  abutments by means of connecting rods on the side walls of the box 14. The curved ends of these hooks are received in complementary recesses formed by deformations formed in the envelope

enclosure 10.

  The sound wave attenuation device operates in the ma-

next.

  Under the control of the excitation circuit and depending on the noise measured

  re by the sensor 32, the loudspeaker 12 emits, inside the enclosure 10, an anti-noise which combines with the proper noise of the exhaust line, this at

  inside the cannula 28. Noise and noise canceling thus canceling out for the most part.

  tiel, the noise emitted by the exhaust line is reduced.

  The presence of a passage established between openings 38 and 72 assu-

  rent the communication of the interior space of the enclosure 10 and

  the interior space of the box 14. The characteristics of this passage (dia-

  meter, length) and of the box 14 are chosen so that their frequency is tuned to the resonant frequency of the loudspeaker. In the device described here, the loudspeaker 12 is kept pressed against the surface 34 of the silencer by the box 14, itself stressed by

the means 16.

  Thus, the loudspeaker 12 is immobilized opposite the opening 36 due to the support of the box 14 via the surfaces 56 and 64, the loudspeaker being, in reaction, supported on the peripheral surface 40 of the enclosure. In such a device, the replacement of the loudspeaker, initially enclosed between the enclosure 10 and the box 14, is very simple since it suffices to

  manually release the biasing means 16 and grasp the top

  speaker which is not attached directly to the enclosure 10 or to the box 14.

  After removing the damaged speaker, a new speaker

  can be engaged through passages 54 and 62 of box 14. The case

  its 14 is then replaced against the enclosure 10 and the means 16 of

  solicitations are locked again.

  In the embodiment described here, the biasing means 16

  are formed by latches. However, these for-

  should be replaced by bolts or any other means of screwing.

Claims (9)

  1.- Device for active attenuation of the sound waves produced by an exhaust line comprising an enclosure (10) for circulation of the exhaust gases, a loudspeaker (12) and means for securing the loudspeaker (12 ) on the enclosure (10), characterized in that the enclosure (10) comprises a wall (34) provided with an opening (36) bordered at its periphery by a surface (40) for support for the top -speaker (12), and in that the securing means comprise a box (14) provided with at least one surface (56, 64) bearing on the loudspeaker (12) and means (16) for solicitation   from the box (14) to the enclosure (10), the loudspeaker (12) being held in   clamped between the enclosure (10) and the box (14).   2.- Active sound wave attenuation device as claimed   cation 1, characterized in that the box (14) has a first wall   (50) provided with a passage (54) for the loudspeaker (12), and in that the loudspeaker   speaker (12) is received at least partially inside the box (14).   3.- Active sound wave attenuation device as claimed   cation 2, characterized in that the first wall (50) has a surface   (56) bearing on the loudspeaker (12) defined at the periphery of the passage (54).   4.- Active sound wave attenuation device as claimed   cation 2 or 3, characterized in that the box (14) has a second wall (52) extending opposite the first wall (50) in the region of the passage (54) delimited in the first wall (50), which second wall   (52) has a bearing surface (64) on the speaker (12).   5.- Active sound wave attenuation device as claimed   cation 3 or 4, characterized in that the or each bearing surface (56, 64) on the loudspeaker (12) and the each corresponding surface (58, 66) of the   loudspeaker (12) have complementary profiles ensuring   essentially tight coupling between the loudspeaker (12) and the or that wall (50, 52) of the box (14).   6.- Active attenuation device for sound waves according to one   conch of the preceding claims, characterized in that the box   (14) has at least one bearing surface (74) on the enclosure (10).   7.- Active sound wave attenuation device as claimed   cation 6, characterized in that the box (14) has a single surface (74) bearing on the enclosure (10).   8.- Active attenuation device for sound waves according to one   conch of the preceding claims, characterized in that it comprises   a passage (38, 72) for connecting the interior spaces of the box (14) and the enclosure (10).   9.- Active attenuation device for sound waves according to one   conch of the preceding claims, characterized in that the means   of the casing (14) towards said enclosure (10) include   snap fastening mechanisms (16).