Patent Publication Number: US-11643953-B2

Title: Exhaust muffler for an exhaust system of an internal combustion engine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C. § 119 of German Application 10 2019 111 270.2, filed May 2, 2019, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention pertains to an exhaust muffler for an exhaust system of an internal combustion engine. 
     TECHNICAL BACKGROUND 
     It is known that Helmholtz resonators are integrated in such exhaust mufflers in order to make it possible to influence the muffling characteristic of exhaust mufflers. Such a Helmholtz resonator comprises in an exhaust muffler a resonator volume in a resonator chamber, which resonator volume is generally basically closed, i.e., no exhaust gas stream passed through the exhaust muffler flows through it, wherein said resonator chamber is open via a resonator neck to the flow volume, through which the exhaust gas stream flows, in the interior of a muffler housing. Adaptation to especially critical or relevant frequencies to be muffled can be carried out by the suitable selection of the volume of the resonator chamber and of the dimension of the resonator neck, especially of the cross-sectional area of an opening of the resonator neck and of the length of the resonator neck. 
     SUMMARY 
     An object of the present invention is to provide an exhaust muffler for an exhaust system of an internal combustion engine, especially in a vehicle, which exhaust muffler provides a broad muffling spectrum with a structurally simple configuration. 
     This object is accomplished according to the present invention by an exhaust muffler for an exhaust system of an internal combustion engine, especially in a vehicle, comprising in a muffler housing:
         a flow volume, through which exhaust gas can flow, with an exhaust gas inlet and with an exhaust gas outlet,   a first resonator chamber, which is open to the flow volume via a first resonator neck,   a second resonator chamber, which is open to the flow volume via a second resonator neck, and   a resonator pipe providing the first resonator neck and the second resonator neck.       

     Two Helmholtz resonators can be built with a single resonator pipe in an exhaust muffler configured according to the present invention, wherein each of these two Helmholtz resonators can be tuned by suitable dimensioning to an especially critical frequency, i.e., the two Helmholtz resonators can consequently be provided with different resonance frequencies. This leads to a muffling spectrum expanded by the use of two Helmholtz resonators with a configuration that can be embodied in a technically simple manner and requires a small number of components. 
     The muffler housing may have a circumferential wall elongated in the direction of a housing longitudinal axis and a front wall each at both axial end areas of the circumferential wall as well as at least two partitions between the front walls, wherein the first resonator chamber is separated by a first partition from the flow volume and the second resonator chamber is separated by a second partition from the flow volume. It should be noted in this connection that the flow volume shall be considered in the sense of the present invention as the volume through which the exhaust gas flows in the interior of the muffler housing and which is provided in one or more chambers and through which the exhaust gas stream flows. The volume of the resonator chambers, which is basically open to this flow volume via the resonator necks and into which exhaust gas can basically also enter via the associated resonator neck, is nevertheless not a part of this flow volume. 
     The flow volume may comprise a flow chamber formed between the first partition and the second partition. This flow chamber may be the only chamber, which is provided in the interior of the muffler housing and through which exhaust gas stream to be passed through the exhaust muffler can flow. It is also possible, however, to provide a plurality of chambers, which communicate with one another via pipes and/or via partitions configured with openings, and through which the exhaust gas stream can flow. 
     To provide a connection of the resonator chambers to the flow volume, it is proposed that the first resonator neck pass through the first partition or/and be open to the first resonator chamber in the area of the first partition, and that the second resonator neck pass through the second partition or/and be open to the second resonator chamber in the area of the second partition. In order to make it possible in this case to efficiently use the volumes of the resonator chambers for the Helmholtz resonators to be provided thereby, provisions are further preferably made for the first partition not to have an opening providing a connection between the flow volume and the first resonator chamber in addition to the opening provided by the first resonator neck and for the second partition not to have an opening providing a connection between the flow volume and the second resonator chamber in addition to the opening provided by the second resonator neck. 
     In order to make it possible in the case of a configuration with a single resonator pipe for two Helmholtz resonators to provide a connection of the resonator necks provided by this resonator pipe with the flow volume, it is proposed that the resonator pipe have at least one pipe wall opening establishing a connection between the flow volume and a pipe interior of the resonator pipe in a pipe wall of the resonator pipe in its section extending in the flow volume. In particular, provisions may be made in this connection for the resonator pipe to have an opening section with a plurality of pipe wall openings in its section extending in the flow volume. 
     The effect of the resonator pipe provided in association with two Helmholtz resonators as two resonator necks can be achieved, for example, by the resonator pipe providing the first resonator neck in a first length area adjoining the opening section at a first axial end area of the opening section and by providing the second resonator neck in a second length area adjoining the opening section at a second axial end area of the opening section. 
     For a compact configuration, the first resonator chamber may be formed between one of the two front walls and the first partition, and the second resonator chamber may be formed between the other of the two front walls and the second partition. 
     Such a compact configuration may be supported by the resonator pipe passing through the flow chamber and being open with a first axial end area to the first resonator chamber or/and by being located in the first resonator chamber and by being open towards the second resonator chamber with a second axial end area or/and by being located in the second resonator chamber and by the resonator pipe having the at least one pipe wall opening in its section extending in the flow chamber. 
     In order to make it possible to introduce the exhaust gas stream to be passed through the exhaust muffler into said exhaust muffler and to remove it again from this, it is proposed that the exhaust gas inlet comprise an inlet pipe that is open in the area of one of the two front walls and comprise an inlet pipe providing an inlet duct, and that the exhaust gas outlet comprise an outlet pipe that is open in the area of the other of the two front walls and provide an outlet duct. 
     To obtain a flow connection with the flow volume or with the flow chamber providing this or an essential part thereof, the inlet pipe may be passed through one of the two resonator chambers, and the outlet pipe may be passed through the other of the two resonator chambers. Provisions may be made in this connection, in particular, for neither the inlet pipe nor the outlet pipe to be open, so that the resonator chambers have, indeed, a connection to the flow volume only through the respective resonator necks associated with these. 
     Further, the inlet pipe may be open to the flow volume in the area of the partition separating one of the two resonator chambers from the flow volume, and the outlet pipe may be open to the flow volume in the area of the housing partition separating the other of the two resonator chambers from the flow volume. 
     In order to make possible the interaction of the resonator pipe provided in association with two Helmholtz resonators with a simple configuration, the first resonator chamber, which is formed between one of the two front walls and the first partition, the flow chamber formed between the first partition and the second partition, and the second resonator chamber formed between the second partition and the other of the two front walls may be provided following each other in the direction of the housing longitudinal axis. 
     In the exhaust muffler according to the present invention, the two Helmholtz resonators, which are provided in it and interact with and are configured with a single resonator pipe, can be tuned to different resonance frequencies in a simple manner by the first resonator chamber and the second resonator chamber having mutually different resonator chamber volumes or/and by the first resonator neck and the second resonator neck having mutually different resonator neck lengths. The resonator pipe could basically also have different cross-sectional dimensions in the areas in which the resonator pipe provides the two resonator necks in order also to influence thereby the resonance frequencies or to be able to provide different resonance frequencies. It is nevertheless proposed for a configuration that can be embodied in a structurally especially simple manner that the resonator pipe have a constant cross-sectional dimension over its entire length, because especially the selection of the length of the resonator necks offers a markedly simpler possibility of influencing the resonance frequencies in the context of the configuration of the resonator pipe. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG.  1    is a sectional view of an exhaust muffler shown in the open state. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings, an exhaust muffler is generally designated by  10  in  FIG.  1   . The exhaust muffler  10  comprises a muffler housing  12  with a circumferential wall  14 , which is elongated in the direction of a housing longitudinal axis A, has, for example, an essentially cylindrical configuration and is made, e.g., of sheet metal material. At both axial ends  16 ,  18 , the circumferential wall  14  is connected in a gastight manner with a respective front wall  20 ,  22 , for example, by connection in substance or/and by positive-locking connection. A first partition  24  and a second partition  26  are connected to the circumferential wall  14 , for example, by connection in substance in an essentially gastight manner in length areas located between the two front walls  20 ,  22 . The front walls  20 ,  22  and the partitions  24 ,  26  are preferably also made of sheet metal material. 
     An exhaust gas inlet generally designated by  28  comprises an inlet pipe  30 , which is connected in an essentially gastight manner to the front wall  20  provided at the axial end area  16  of the circumferential wall  14 , on the one hand, and to the first partition  24 , on the other hand, and it provides in its interior an inlet duct  34  leading to a flow chamber  32 . The inlet pipe  30  thus forms in the area of the front wall  20  an inlet opening of the exhaust gas inlet  28 , which said inlet opening is open towards the inlet duct  34 . In the area of the first partition  24 , the inlet pipe  30  is open towards the flow chamber  32 . It should be noted that the inlet pipe  30  ends in the area of the first partition  24  in the exemplary embodiment shown. This inlet pipe  30  could also extend beyond the first partition  24  into the flow chamber  32 . 
     An exhaust gas outlet generally designated by  36  comprises an outlet pipe  38  connected in a gastight manner to the second partition  26 , on the one hand, and to the front wall  22  provided at the axial end area  18  of the circumferential wall  14 , on the other hand. An outlet duct  40 , via which exhaust gas flowing through the flow chamber  32  can leave the exhaust muffler  10 , is formed in the outlet pipe  38 . In the area of the front wall  22 , the outlet pipe  38  with its outlet duct  40  is open to the environment or to an area of an exhaust system following in the flow direction. In the area of the second partition  26 , the outlet pipe  38  is connected to this partition  26  and is open towards the flow chamber  32 . It should be noted here as well that, unlike as it is shown, the outlet pipe  38  could extend into the flow chamber  32  beyond the second partition  26 . Further, it should be noted that both the inlet pipe  30  and the outlet pipe  38  may extend out of the muffler housing  12  via the front walls  20  and  22 , respectively, which are connected to the inlet pipe  30 , and the outlet pipe  38 , in order to make it possible to facilitate a connection to areas of an exhaust system which follow upstream and downstream. 
     In the example shown, the inlet duct  34 , the outlet duct  40  and the flow chamber  32  provide a flow volume  42  through which exhaust gas to be sent through the exhaust muffler can flow. In addition to this flow volume  42 , two resonator chambers  44 ,  46  are integrated into the exhaust muffler  10 . The first resonator chamber  44 , which is formed between the front wall  20  and the first partition  24 , i.e., which is defined essentially axially by these walls, is associated with a first Helmholtz resonator  48 . The second resonator chamber  46 , which is formed between the second partition  26  and the front wall  22 , i.e., which is defined essentially by these axially, is associated with a second Helmholtz resonator  50 . The inlet pipe  30  passes in this case through the first resonator chamber  44 , and the inlet pipe  30  does not provide an opening that is open towards the first resonator chamber  44 , i.e., it is consequently closed with respect to this. The outlet pipe  38  passes through the second resonator chamber  46  and likewise has no opening that is open towards this, so that the outlet pipe  38  is basically closed against the second resonator chamber  46 . 
     A resonator pipe generally designated by  52  is provided in the interior of the muffler housing  12 . The resonator pipe  52  has basically three length areas  54 ,  56 ,  58  adjoining one another in the direction of the housing longitudinal axis A. The length area  54  of the resonator pipe  52 , which length area is positioned approximately in the central part of the longitudinal area of the resonator pipe  52 , provides an opening section  60 , in which the resonator pipe  52  or a pipe interior formed therein is open via a plurality of pipe wall openings  64  provided in a pipe wall  62  of the resonator pipe  52  towards the flow chamber  32  and towards the flow volume  42 . The pipe wall openings  64  may be arranged, for example, in a plurality of rows of openings extending in the direction of the housing longitudinal axis A in an essentially regular pattern of openings and thus establish in the circumferential direction of the pipe wall  62  of the resonator pipe  52  an essentially uniformly acting connection between the interior of the pipe and the flow chamber  32 . 
     The length area  56  adjoining in an axial end area  66  of the opening section  60 , which end area is located closer to the first partition  24 , forms a first resonator neck  68  of the first Helmholtz resonator  48 . The length area  56  or the first resonator neck  68  provided by this length area  56  passes through an opening in the first partition  24  and is preferably connected to this in an essentially gastight manner. In a first axial end area  70  of the resonator pipe  52 , which end area  70  is positioned such that it meshes, extending beyond the first partition  24  in the example shown, with the first resonator chamber  44 , the resonator pipe  52  or the first resonator neck  68  is open towards the first resonator chamber  44  and it provides in connection with this essentially the first Helmholtz resonator  48 . In addition to the opening provided for or receiving the length area  56  of the resonator pipe  52 , the first partition  24  has no additional openings establishing a connection between the first resonator chamber  44  and the flow volume or the flow chamber  32  thereof. 
     The length area  58  of the resonator pipe  52 , which length area adjoins a second axial end area  72  of the opening section  60 , passes through an opening in the second partition  26  and is connected to this preferably in an essentially gastight manner. The length area  58  forms a second resonator neck  74  and is open in the area of a second axial end area  76  of the resonator pipe  52  towards the second resonator chamber  46 . The second length area  58  extends beyond the second partition  26 , meshing with the second resonator chamber  46 , and it provides in connection with this essentially the second Helmholtz resonator  50 . This second partition  26  also has, in addition to the opening through which the resonator pipe  52  passes, no additional openings that provide a connection between the second resonator chamber  46  and the flow volume  42  or the flow chamber  32 . 
     An acoustic connection of the two Helmholtz resonators  48 ,  50  or of the resonator necks  68 ,  74  thereof to the flow volume  42  or to the exhaust gas flowing through the flow volume  42  and generating sound is brought about via the pipe wall openings  64 . Even though this exhaust gas will also fill the pipe interior of the resonator pipe  52 , neither the volumes  44 ,  46  nor the pipe interior of the resonator pipe  52  participate in the exhaust gas flow, with the exception of the flow cross section  54  through which exhaust gas can basically flow, and therefore they shall not be considered to be a part of the flow volume in the sense of the present invention, either. 
     The resonance frequencies of the two Helmholtz resonators  48 ,  50  can be set and tuned in a defined manner to especially critical frequencies by the selection of the volumes of the two resonator chambers  44 ,  46 , which volumes are limited essentially by the front walls  20 ,  22  and partitions  24 ,  26  axially limiting the resonator chambers  44 ,  46  as well as by the circumferential wall  14 , and from which the volume occupied by the inlet pipe  30  and by the outlet pipe  38  shall always be subtracted, and by the correspondingly suitable dimensioning of the resonator necks  68 ,  74 . It can be recognized now that with an especially simple structural configuration, the resonator pipe  52  is configured with essentially constant cross-sectional dimension, i.e., especially also with constant internal diameter in the direction of the housing longitudinal axis A, so that the particular resonance frequency of the Helmholtz resonators is influenced in the area of the resonator necks  68 ,  74  essentially by the suitable selection of the length thereof. This can, in turn, be brought about by the opening section  54  being arranged in a suitable positioning between the two axial end areas  70 ,  76  of the resonator  52 , but within the axial extension of the resonator chamber  32  and also with a suitable extension in the direction of the housing longitudinal axis A. The longer the opening section  54  of the resonator pipe  52 , the shorter is the still available length of the two length areas  56 ,  58  providing the resonator necks  68 ,  76 . 
     Due to the fact that in the configuration according to the present invention, the two resonator chambers  44 ,  46  are arranged axially each directly adjoining the flow volume  42  through which the resonator pipe  52  passes, especially the flow chamber  32 , an axially compact configuration is obtained, on the one hand, and it is made possible, on the other hand, for the single resonator pipe  52  to be able to provide the resonator necks  68 ,  74  associated with the two Helmholtz resonators  48 ,  50 . 
     It should be noted in this connection that this can also be achieved if the flow volume has a plurality of flow chambers. For example, an additional partition, in which, for example, a connection is established between these chambers through one or more openings or/and one or more pipes pass through these, could be provided between the two partitions  24 ,  26 , so that the exhaust gas flowing from the inlet  28  to the outlet  36  can flow through all these chambers. The opening section  54  could be arranged now in one of these chambers or it could be arranged located in both chambers or be divided into two areas, each of which is positioned in one of the flow chambers to be included in the flow volume  42 . However, no additional partition dividing the flow volume  42  into a plurality of chambers is provided between the first partition  24  and the second partition  26  in the especially preferred type of configuration shown. The exhaust gas outlet could also have, for example, a plurality of outlet pipes, which would form, for example, respective tail pipes in this case. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.