Silencer for a motor vehicle exhaust system, and its method of mounting

Abstract

A silencer for a vehicle engine exhaust system, wherein the silencer is constituted by at least one duct which acts as a guide for exhaust gas and as an acoustic attenuator for exhaust noise, and which comprises at least one porous internal metal tubular element, intermediate thermal and acoustic lagging, and a leaktight outer covering of polymer material, and wherein the outer covering is connected in leaktight manner to two tubular metal connection devices via two metal caps.

1 . A silencer for a vehicle engine exhaust system, wherein the silencer is constituted by at least one duct which acts as a guide for exhaust gas and as an acoustic attenuator for exhaust noise, and which comprises at least one porous internal metal tubular element, intermediate thermal and acoustic lagging, and a leaktight outer covering of polymer material, and wherein the outer covering is connected in leaktight manner to two tubular metal connection devices via two metal caps.  
     
     
         2 . A silencer according to  claim 1 , in which the duct is flexible.  
     
     
         3 . A silencer according to  claim 1 , in which the internal metal tubular element is constituted by a flat spring having overlapping turns.  
     
     
         4 . A silencer according to  claim 1 , in which the internal metal tubular element is constituted by a sheet metal tube with single or double seam joints.  
     
     
         5 . A silencer according to  claim 1 , in which the flexible or rigid internal metal tubular element is pierced by openings.  
     
     
         6 . A silencer according to  claim 5 , in which the openings are of diameter that increases in the flow direction of the exhaust gas.  
     
     
         7 . A silencer according to  claim 6 , in which the openings are subdivided into a plurality of series of openings, the openings in each series having substantially the same diameter.  
     
     
         8 . A silencer according to  claim 5 , in which the internal metal tubular element is constituted by at least two concentric tubes, an inner tube and an outer tube, both pierced by openings.  
     
     
         9 . A silencer according to  claim 8 , in which the inner metal tube extends over a portion only of the total length of the silencer.  
     
     
         10 . A silencer according to  claim 1 , in which the internal tubular element is covered in a refractory fabric presenting a degree of porosity.  
     
     
         11 . A silencer according to  claim 10 , in which the refractory fabric is made of ceramic, basalt, or glass fibers.  
     
     
         12 . A silencer according to  claim 1 , in which the outer covering of the duct is made on the basis of a thermoplastic material such as polyamide  66 , or on the basis of an elastomer material such as Vamac®, or a silicone.  
     
     
         13 . A silencer according to  claim 1 , in which the outer covering of the duct is formed by a blow extrusion operation.  
     
     
         14 . A silencer according to  claim 1 , in which leaktight annular volumes are formed that are spaced apart longitudinally in the thermal and acoustic lagging.  
     
     
         15 . A silencer according to  claim 14 , in which each leaktight intermediate volume in the thermal and acoustic lagging is defined by two compression rings.  
     
     
         16 . A silencer according to  claim 15 , in which each compression ring is resilient and made of silicone, for example.  
     
     
         17 . A silencer according to  claim 1 , in which acoustic baffles are interposed in the internal tubular element of the flexible duct.  
     
     
         18 . A silencer according to  claim 17 , in which an acoustic baffle is constituted by three disks mounted perpendicularly to the exhaust gas flow axis, and by two connection tubes presenting holes that are coaxial with the internal tubular element and that are of smaller diameter.  
     
     
         19 . A silencer according to  claim 1 , in which the leakproof outer covering presents at least one outwardly-directed projection to create an additional volume which is filled with the material forming the lagging.  
     
     
         20 . A silencer according to  claim 19 , in which the inside wall of the projection is covered in an absorbent lining.  
     
     
         21 . A silencer according to  claim 20 , in which the absorbent lining is a cellular silicone foam.  
     
     
         22 . A silencer according to  claim 1 , in which the flexible duct has its entrance connected to a flared tubular metal connection device presenting internal and/or external cooling fins to reduce the temperature of the exhaust gas.  
     
     
         23 . A silencer according to  claim 1 , in which the flexible duct is connected at its exit to a diffuser-forming device for reducing the exit temperature of the exhaust gas.  
     
     
         24 . A silencer according to  claim 23 , in which the diffuser-forming exit device comprises at least one generally conical element that is pierced by holes, and a tubular exit element which surrounds and extends the element, and having a wall that presents at least one opening for enabling ambient air to enter therein.  
     
     
         25 . A silencer according to  claim 23 , in which the diffuser-forming exit device comprises at least one star-shaped element and an exit tubular element which surrounds and extends the element, and having a wall that presents at least one opening for allowing ambient air to enter therein.  
     
     
         26 . A silencer according to  claim 1 , in which the leakproof outer covering of the silencer forms a box through which the internal metal tubular element passes, the intermediate thermal and acoustic lagging filling said box.  
     
     
         27 . A silencer according to  claim 26 , in which the internal metal tubular element forms at least one bend inside the box.  
     
     
         28 . A silencer according to  claim 26 , in which the box presents in its wall, at least one surface formed by a resonant membrane which is tuned to at least one frequency in the frequency spectrum to be attenuated.  
     
     
         29 . A silencer according to  claim 1 , in which the silencer comprises at least two ducts connected to each other by an optionally bent tubular metal element.  
     
     
         30 . A silencer according to  claim 29 , in which the tubular metal element is smooth.  
     
     
         31 . A method of mounting a silencer as defined in  claim 1  in a motor vehicle exhaust system, the method consisting in manufacturing, storing, and transporting the silencer in rectilinear shape, in deforming it to take up a given configuration at the time it is mounted in the exhaust system, and in fastening it to the vehicle body by means of rigid fastening tabs.  
     
     
         32 . A method according to  claim 31 , in which the duct is bent at a corrugated zone of the duct.  
     
     
         33 . A method according to  claim 31 , in which the leakproof outer covering of the duct is made by a blow extrusion operation.