Patent Publication Number: US-2015071452-A1

Title: Active sound generation device

Description:
The present invention relates to a sound generation device for exhaust gas systems of motor vehicles having a housing and a sound generating means, in particular a loudspeaker, arranged in the housing with a closed sound generation surface and a margin tightly enclosing the noise generation surface. 
     The generation of sound or anti-sound or of other sounds for the acoustic influencing of engine sound requires inter alia an exact configuration of the front volume and rear volume of the activator housing which have to be comparatively large, at least with internal combustion engines, to achieve a sufficient sound absorption or sound influencing by modulating the engine sound. Since each engine type has a different characteristic with respect to the generated sound pressure level and since elements connected to the engine can also have an acoustic effect, the acoustic effect of the active sound generation system has to be configured separately for each motorization. 
     It is the underlying object of the invention to meet these demands. 
     This object is satisfied by the independent claims. The dependent claims relate to advantageous further developments of the invention. 
     In accordance with claim  1 , the object is in particular satisfied in that the housing has an at least sectionally cylindrical shape and in that the inner diameter of the cylindrical shape corresponds to the projection of the outer periphery of the margin surrounding the sound generation system onto a surface perpendicular to the cylinder axis such that the sound generation means can be inserted in a gas-tight manner at any desired point of the cylindrical section. 
     The ratio of front volume and rear volume of the sound generation device can be varied by the possibility of arranging the sound generation means at any desired point of the cylindrical section. It is thereby possible to use one and the same housing for different motorizations. Costs are thus saved. The gas-tightness can be achieved, for example, by welding or brazing the margin to the cylindrical section. It effects the separation of the front volume and rear volume, that is of the housing volume before and behind the sound generation surface. The housing can, for example, comprise shells or can be configured as a wrap housing. 
     The housing preferably has a middle cylindrical section which is closed at both sides by arched termination walls which are preferably formed as identical parts. This housing shape has proved to be particularly advantageous, with the use of identical parts further lowering the costs. 
     The outer periphery of the margin of the sound generation means can be at least approximately circular, oval or elliptical. The housing can advantageously be configured as flatter in one direction by ab oval or elliptical shape. The small construction space beneath a vehicle floor can thus be taken into account. 
     An adapter ring is preferably provided which forms at least the outermost part of the margin of the sound generation means. The adapter ring can be releasably or non-releasably connected to the sound generation surface. It allows a good adaptation of the sound generation means to the housing shape independently of the outer periphery of the sound generation surface. The adapter ring can be fixedly connected to the housing, for example by welding. 
     In accordance with a further embodiment of the invention, the sound generation surface can be inclined in at least one direction with respect to the longitudinal axis of the cylindrical section of the housing. The construction space of the housing can thus be further reduced with the same sound output surface of the sound generation means. 
     In accordance with the second independent claim, the housing is formed by two half-shells, with the sound generation surface extending transversely or inclined with respect to the separation plane of the two half-shells. An inexpensive construction of the housing hereby results. 
     The sound generation surface preferably passes through the separation plane of the two half-shells. A good utilization of the construction space thereby results together with the possibility of selecting the front volume and rear volume of the actuator housing in a suitable manner. It is further preferred if the margin of the sound generation surface is connected to both half-shells, in particular directly or in particular not via the respective other half-shell. The volume of the actuator housing is thereby divided into a front volume and rear volume substantially transversely to the separation plane. 
     In accordance with an embodiment of the invention, the sound generation means can be clamped between the two half-shells, in particular by means of a bead running around both half-shells. The manufacturing costs can thereby be further reduced. Sealing material is preferably inserted into the bead for the separation of the front volume and the rear volume. The sound generation means can, however, also be connected in a gas-tight manner to the two half-shells in another manner, for example by welding or brazing. 
     In accordance with another embodiment of the invention, the sound generation means is screwed to a first flange provided at one half-shell, whereas a second flange is provided at the other half-shell which contacts the sound generation means in the assembled state of the half-shells and surrounds said sound generation means together with the first flange in a gas-tight manner to form a rear volume and a front volume. An inexpensive construction also hereby results. 
     In accordance with yet another embodiment of the invention, the sound generation means is connected to a half-shell by means of a clip, whereas the margin of the sound generation means is connected to the half-shells in a gas-tight manner by welding to form a front volume and a rear volume. This construction is also inexpensive. 
     In accordance with a further embodiment of the invention, the sound generation means, in particular the magnet of a loudspeaker, is additionally supported with respect to the housing via at least one further device, in particular a ferromagnetic or paramagnetic bracket. A more stable construction thereby results. The additional device can be connected to the loudspeaker magnet purely magnetically due to the use of a ferromagnetic or paramagnetic bracket, whereby separate connection elements can be saved. 
     The further device for supporting the sound generation means can also be configured for leading heat off from the sound generation means to the housing. An overheating of the sound generation means can thus be avoided. 
     In accordance with a further embodiment of the invention, the housing has a receiver for at least a part of the magnet of a loudspeaker. In this respect, can also only be a wall section of the housing which the magnet contacts. A further support of the sound generation means is produced via this receiver, whereby the stability of the construction is further increased. 
     In accordance with a further embodiment of the invention, a pipe is provided which conducts the generated sound out of the housing and to a sound superimposition location. In this respect, the pipe can preferably be bent at least once. The thermal separation of the housing from the exhaust gas system is thus improved, on the one hand, and larger objects cannot penetrate into the housing so easily, on the other hand. Another possibility of avoiding a penetration of objects into the housing comprises a barrier, for example a mixer or another slightly gas permeable element such as a grid or the like which is installed in the pipe. 
     The thermal separation from the exhaust gas system can in turn be improved by a particularly long pipe. Another possibility comprises making the pipe short and connecting it to the exhaust gas system via a thermally insulated connection. A mechanical decoupling between the housing and the exhaust gas system by a so-called decoupling element, for example by a bellows in the exhaust pipe, is likewise advantageous. 
     In accordance with a particular embodiment of the invention, the active sound generation device can be connected to the exhaust gas system via a double opening. In this case, a pipe connection is preferably provided between the two parts of the double opening and a sensor for measuring the pressure difference between the two parts is arranged in said pipe connection. The superimposition of engine sound and generated sound, for example disturbing noise and anti-sound, can thus be measured by only one sensor and can be used for the regulation of the active sound absorption device. 
     The housing can moreover be provided with an outlet opening which opens to the outside or with a suction pipe for condensed water. The suction pipe is in this respect connected at its second end to an exhaust pipe of the exhaust gas system. Condensed water is sucked out of the housing via the suction pipe due to the pressure difference between the exhaust gas system and the housing. 
    
    
     
       Embodiments of the invention are shown in the drawings and will be described in the following. There are shown, schematically in each case 
         FIGS. 1   a  and  b  a first embodiment of the invention with two different installation positions; 
         FIG. 2  a second embodiment of the invention with a housing comprising two half-shells; 
         FIG. 3  a variant of  FIG. 2 ; 
         FIG. 4  a further variant of  FIG. 2 ; 
         FIGS. 5   a  and  b  different inclination possibilities of a loudspeaker in a housing; 
         FIGS. 6   a  and  b  two combining possibilities for the pipe led out of the housing and an exhaust pipe of the exhaust gas system; 
         FIGS. 7   a  and  7   b  a double-opening section with a pipe connection and a sensor in a plan view and in cross-section; and 
         FIGS. 8   a  to  c  three further combinations between the active sound absorber and the exhaust gas system. 
     
    
    
     The sound generation device shown in  FIG. 1  comprises a housing  1  with a middle cylindrical section  2  and two arched termination walls  3  which are arranged at both sides thereof and which are formed as identical parts. A loudspeaker  4 , whose membrane  5  forms a sound generation surface, is arranged in the housing  1 . The membrane  5  is radially outwardly surrounded by an adapter ring  6  which is fixedly connected, in particular welded, to the housing  1  and which is formed in a gas-tight manner with respect to the membrane  5 . In this manner, the inner space of the housing  1  is divided by the loudspeaker  4  and the adapter ring  6  into a front volume  7  and a rear volume  8 . The ratio of front volume and rear volume can be set as required by displacing the loudspeaker  4  along the cylindrical section  2  in accordance with the double arrow. 
     A reflex tube  9  which is formed as curved is led out of the front volume  7 . A penetration of objects into the housing  1  is made difficult thereby. Furthermore, the magnet  10  of the loudspeaker  4  is additionally supported with respect to the housing  1  via a bracket  11 . The bracket  11  is ferromagnetic or paramagnetic so that no additional fastening is required. Alternatively or additionally, cross-struts  11 ′ can be provided between the loudspeaker magnet  10  and the housing  1 . 
     The cross-section of the loudspeaker membrane  5  and of the adapter ring  6  as well as the cylindrical section  2  of the housing  1  can in particular be circular, oval or elliptical. The height can thus be reduced with respect to the width of the housing  1 . Furthermore, as shown in  FIGS. 5   a  and  5   b , the loudspeaker can be inclined in one or two mutually perpendicular directions with respect to the longitudinal axis I of the cylindrical section  2 . This results in each case in a reduced cross-section of the housing  1  with an unchanged sound output surface, as results from a comparison of the dimensions A, B or C, D. 
     In the variants of the invention shown in  FIGS. 2 to 4 , the housing comprises two half-shells, namely an upper shell  12  and a lower shell  13 . In the variant shown in  FIG. 2 , the loudspeaker  4  is clamped between the two half-shells by means of a bead  14  running around over the upper shell  12  and the lower shell  13 . The loudspeaker  4  is additionally supported via a further bead  15  in the lower shell  13 . A further support is provided via a ferritic holder  16 . 
     In the variant shown in  FIG. 3 , a respective flange  17 ,  18  is provided in the upper shell  12  and the lower shell  13  respectively. The loudspeaker  4  is screwed to the flange  18  of the lower arm  13  via its peripheral margin  6 , with the flange being arranged on the rear side of the margin  6 . The flange  17  of the upper shell  12  contacts the margin  6  of the loudspeaker  4  from the front with an assembled housing  1  and forms, together with the flange  18 , a gas-tight seal of the loudspeaker  4  with respect to the housing  1 . The magnet  10  of the loudspeaker  4  moreover contacts a support surface  19  of the lower shell  13 . The reflex tube  9  is led out of the housing  1  with a slope, which is also advantageous in all other embodiments of the invention. 
     In the variant shown in  FIG. 4 , the loudspeaker  4  is connected via a clip  20  to the lower shell  13 . The margin  6  of the loudspeaker  4  is connected in a gas-tight manner to the upper shell  12  and to the lower shell  13  by laser welding. The lower shell  13  moreover has a hole  21  for the draining of condensed water. Instead of a hole, a suction pipe  31 , as shown in  FIG. 2 , can also be provided for sucking off condensed water, the suction pipe being connected at its other end to an exhaust pipe  22  of the exhaust gas system. Both variants can be used in all embodiments of the invention. 
       FIG. 6  shows the combination of a reflex tube  9  of a sound generation device in accordance with the invention with an exhaust pipe  22  of an exhaust gas system. In  FIG. 6   a , the combination is configured in funnel shape, whereas it is cylindrical in  FIG. 6   b . The combination can itself form the opening of the exhaust gas system or can be connected to a separate opening via a pipe. 
       FIG. 7  shows a double opening  23  of a reflex tube  9  of a sound generation device in accordance with the invention and of an exhaust pipe  22  of an exhaust gas system. The two pipes  9 ,  22  are connected to one another via a pipe connection  24 . The pressure difference between the reflex tube  9  and the exhaust pipe  22  can be determined via a sensor  25  in the pipe connection  24  and can be used for the regulation of the anti-sound generation. Alternatively, a sensor can respectively also be provided in the reflex tube  9  and in the exhaust pipe  22 . 
       FIG. 8   a  shows another combination of an active sound generation device in accordance with the invention and of an exhaust pipe  22 . As can be seen, the reflex pipe  9  is curved a multiple of times and is combined with the exhaust pipe  22 . The active sound generation device is additionally supported with respect to the exhaust gas system via a rubber pendulum bearing. 
     The reflex tube  9  is short in the variant of a combination of a sound generation device in accordance with the invention shown in  FIG. 8   b  with the exhaust pipe of an exhaust gas system. The combination is configured with air-gap insulation for the thermal decoupling of the active sound generation device from the exhaust gas system. Furthermore, a decoupling element  27  in the form of a bellows section is provided for the mechanical decoupling of the active sound generation device from the exhaust gas system. A grid  28  which prevents a penetration of objects can be provided between the reflex tube  9  and the housing  1  (see  FIG. 4 ). 
     In the variant shown in  FIG. 8   b , the opening of the reflex pipe  9  into the exhaust pipe  22  likewise has air gap insulation. A mixer  30  which prevents a penetration of objects is arranged in the continuing exhaust pipe  29 . 
     REFERENCE NUMERAL LIST 
     
         
           1  housing 
           2  cylindrical section 
           3  termination wall 
           4  loudspeaker 
           5  loudspeaker membrane 
           6  adapter ring 
           7  front volume 
           8  back volume 
           9  reflex tube 
           10  loudspeaker magnet 
           11  bracket 
           11 ′ cross-strut 
           12  upper shell 
           13  lower shell 
           14  bead 
           15  bead 
           16  holder 
           17  flange 
           18  flange 
           19  support surface 
           20  clip 
           21  hole 
           22  exhaust pipe 
           23  double opening 
           24  connection pipe 
           25  sensor 
           26  rubber pendulum bearing 
           27  decoupling element 
           28  grid 
           29  continuing exhaust pipe 
           30  mixer 
           31  suction pipe 
         I longitudinal axis of  2   
         II separation plane