Exhaust chamber comprising an envelope defining a gas circulation passage

Abstract

An exhaust chamber includes an external envelope ( 10 ), defining a gas circulation passage and at least one continuous wall ( 16, 20, 22, 24 ) along which at least one cover piece ( 26 A, 26 B, 30, 32, 34 ) is arranged, the or each cover piece ( 26 A, 26 B, 30, 32, 34 ) only extending over a limited region of the continuous wall. The dimensions of the cover piece ( 26 A, 26 B, 30, 32, 34 ) and the connection between the cover piece and the continuous wall are selected such that for at least one excitation frequency in the exhaust chamber between 200 Hz and 4 kHz inclusive the cover piece and the continuous wall vibrate with a phase shift of at least 90°. The above finds application in the field of automobile exhausts.

1 - 16 . (canceled)  
   
   
       17 . Exhaust chamber comprising an external envelope delimiting a gas circulation passage and comprising at least one continuous wall, along which at least one cover piece is arranged, the cover piece or each cover piece only extending over a small, limited region of said continuous wall, characterised in that the dimensions of the cover piece and the connection between the cover piece and the continuous wall are such that, for at least one excitation frequency in the exhaust chamber between 200 Hz and 4 kHz, the cover piece and the continuous wall vibrate with a phase shift greater than 90°.  
   
   
       18 . Exhaust chamber according to  claim 17 , characterised in that the total area of the continuous wall that is covered by the cover piece or each cover piece is between 10% and 50% of the total area of said continuous wall.  
   
   
       19 . Exhaust chamber according to  claim 17 , characterised in that the dimensions of the cover piece and the connection between the cover piece and the continuous wall are such that, for at least one excitation frequency in the exhaust chamber between 200 Hz and 4 kHz, the cover piece and the continuous wall vibrate in phase opposition.  
   
   
       20 . Exhaust chamber according to  claim 17 , characterised in that the dimensions of the cover piece and the connection between the cover piece and the continuous wall are such that, for at least one excitation frequency in the exhaust chamber between 200 Hz and 4 kHz, the cover piece and the continuous wall vibrate with a phase shift between 90° and 270° for at least 20% of the frequencies.  
   
   
       21 . Exhaust chamber according to  claim 17 , characterised in that said continuous wall is a substantially smooth free wall.  
   
   
       22 . Exhaust chamber according to  claim 17 , characterised in that a single cover piece is arranged on a continuous wall, and in that said limited region, along which said cover piece is arranged, extends approximately in the centre of the evolute of said continuous wall.  
   
   
       23 . Exhaust chamber according to of  claim 17 , characterised in that it comprises at least two cover pieces arranged on a continuous wall, and in that the barycentre of the cover pieces is located approximately in the centre of the evolute of said continuous surface.  
   
   
       24 . Exhaust chamber according to  claim 17 , characterised in that it comprises a transverse wall arranged inside said envelope and delimiting therein two adjacent chambers, and in that said cover piece is arranged along said transverse wall.  
   
   
       25 . Exhaust chamber according to  claim 17 , characterised in that said cover piece is arranged along said external envelope.  
   
   
       26 . Exhaust chamber according to  claim 25 , characterised in that said external envelope comprises at least two half-shells that are joined along a joint, and in that said cover piece is joined to the two half-shells in at least two regions of said joint.  
   
   
       27 . Exhaust chamber according to  claim 17 , characterised in that said cover piece is welded over at least a part of its periphery to said wall.  
   
   
       28 . Exhaust chamber according to  claim 17 , characterised in that said continuous wall has a basin in which said cover piece is confined.  
   
   
       29 . Exhaust chamber according to  claim 17 , characterised in that it comprises a damping material inserted between the wall and the cover piece.  
   
   
       30 . Exhaust chamber according to  claim 17 , characterised in that, over most of its area, said cover piece is juxtaposed against said continuous wall.  
   
   
       31 . Use for reducing the sound emissions of an exhaust chamber comprising an external envelope delimiting a gas circulation passage, and comprising at least one continuous wall, at least one cover piece arranged along the continuous wall, the cover piece or each cover piece only extending over a small, limited region of said continuous wall, the dimensions of the cover piece and the connection between the cover piece and the continuous wall being such that, for at least one excitation frequency in the exhaust chamber between 200 Hz and 4 kHz, the cover piece and the continuous wall vibrate with a phase shift greater than 90°.  
   
   
       32 . Use according to  claim 31 , characterised in that the total area of the continuous wall that is covered by the cover piece or each cover piece is between 10% and 50% of the total area of said continuous wall.