Abstract:
A passive, exhaust pressure actuated valve assembly for placement inside a tubular exhaust conduit is pivotally mounted to an off-center axle for rotation between fully closed and fully opened positions. A bias element forces the valve flap toward the fully closed position. The valve flap is shaped in a manner enabling use of the interior surface of the exhaust conduit to define stops at the full closed and full opened positions. The valve flap shape, in conjunction with the bias element arrangement, enables the flap to lie substantially parallel to a longitudinal axis of the conduit in the fully opened position, which provides for minimum back pressure in the conduit. The valve assembly finds particularly advantageous use inside a bypass through pipe of a muffler assembly.

Description:
RELATED APPLICATION 
   This is a continuation-in-part of commonly owned U.S. application Ser. No. 11/687,151 filed Mar. 16, 2007, the disclosure of which is incorporated herein by reference in its entirety. 

   BACKGROUND 
   Field 
   The invention generally relates to valve arrangements for vehicle exhaust systems. More specifically, the present teachings pertain to passive flapper valves for exhaust conduits. 
   Many exhaust systems have attempted to use both active and passive valve assemblies to alter the characteristics of exhaust flow through a conduit as the exhaust pressure increases due to increasing engine speed. Active valves carry the increased expense of requiring a specific actuating element, such as a solenoid. Passive valves utilize the pressure of the exhaust stream in the conduit with which the valve is associated. 
   Traditionally, even passive valves at their lower expense give rise to problems of unwanted back pressure when the valve is open. There is seen to be a need in the art for a passive valve arrangement which may be utilized totally inside a conduit, which is relatively inexpensive, and is capable of assuming a fully open position which minimizes unwanted back pressure. 
   SUMMARY 
   In one aspect of the disclosed teachings, a muffler for an internal combustion engine exhaust system includes a housing having an outer shell and input and output headers enclosing opposite ends of the shell. At least one partition inside the housing divides a housing interior into first and second chambers. At least one of the chambers has sound absorbing material positioned therein, the at least one partition having at least one aperture therethrough providing for fluid communication between the first and second chambers. A through pipe extends through the input and output headers and the at least one partition and has a plurality of perforations enabling fluid communication between the through pipe and the first chamber. A valve assembly has a valve flap positioned inside the through pipe for rotation about an axle pivotally coupled to the pipe between a fully closed position wherein a first peripheral portion of the valve flap is in contact with an inner surface of the through pipe and a fully open position wherein a plane of the valve flap is substantially parallel to a longitudinal axis of the through pipe and a second peripheral portion of the valve flap is in contact with an inner surface of the through pipe. 
   In another aspect of the disclosed teachings, a muffler for an internal combustion engine exhaust system includes a housing having an outer shell and input and output headers enclosing opposite ends of the shell. First and second partitions inside the housing divide a housing interior into first, second and third chambers, the first chamber defined by the first partition and the input header, the second chamber defined by the second partition and the output header, and the first and second partitions defining the third chamber therebetween. The first and second partitions have at least one aperture therethrough providing fluid communication between the first and second chambers via the third chamber. The first and second chambers each have sound absorbing material positioned therein. A through pipe extends through the input and output headers and the first and second partitions and has a first plurality of partitions enabling fluid communication between the through pipe and the first chamber, and a second plurality of perforations enabling fluid communication between the through pipe and the second chamber. A valve assembly has a valve flap positioned inside the through pipe in the third chamber between the first and second pluralities of through pipe perforations for rotation about an axle pivotally coupled to the pipe between a fully closed position wherein a first peripheral portion of the valve flap is in contact with an inner surface of the through pipe and a fully open position wherein a plane of the valve is substantially parallel to a longitudinal axis of the through pipe and a second peripheral portion of the valve flap is in contact with an inner surface of the through pipe. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The objects and features of the disclosed teaching will become apparent from a reading of the detailed description, taken in conjunction with the drawing, in which: 
       FIGS. 1A ,  1 B are respective side and end views of a valve controlling fluid flow through a conduit, the valve being in a closed position and arranged in accordance with the disclosed teachings; 
       FIGS. 2A ,  2 B are respective side and end views of the valve of  FIGS. 1A ,  1 B in a 15° open position; 
       FIGS. 3A ,  3 B are respective side and end views of the valve of  FIGS. 1A ,  1 B in a 30° open position; 
       FIGS. 4A ,  4 B are respective side and end views of the valve of  FIGS. 1A ,  1 B in a fully open position; 
       FIGS. 5A ,  5 B are respective side and end views of a first valve axle arrangement in accordance with the present teachings; 
       FIGS. 6A ,  6 B are respective side and end views of a second valve axle arrangement in accordance with the present teachings; 
       FIG. 7  is an end view of the valve of  FIGS. 1A and 1B  with the pipe contacting the valve flap altered to achieve substantially full blockage of the pipe when the valve is placed in the fully closed position; 
       FIG. 8  is a side cross-sectional view of an exhaust muffler arranged with the valve of  FIGS. 1A ,  1 B in accordance with the present teachings; 
       FIG. 9  is a side cross-sectional view of a first alternative embodiment of an exhaust muffler arranged with a flapper valve in accordance with the present teachings; and 
       FIG. 10  is a side cross-sectional view of a second alternative embodiment of an exhaust muffler arranged with a flapper valve in accordance with the present teachings. 
   

   DETAILED DESCRIPTION 
   With reference to  FIGS. 1A-4B , side and end views of a valve assembly with a valve flap in various operative positions is shown in side and end views of the conduit in which the valve assembly is positioned. Identical elements among these Figures carry the same last two designation numerals. 
   An exhaust conduit  102  contains a snap-action valve  100  which includes a spring anchor  104 , a valve spring  106 , an external lever arm  108 , a valve flap  110 , a valve support shaft or axle  112  and a spring attachment arm  114  protruding from axle  112 . 
   Valve flap  110  has first and second arcuate edges substantially conforming to an interior arcuate surface of conduit  102 . Flapper  110  additionally has linear side edges  116  and  118  which provide clearance  120 ,  122  between flapper  110  and an interior surface of conduit  102  when the flap is in the closed position shown in  FIGS. 1A and 1B . Bias element or spring  106  extends between an anchor point  104  on conduit  102  and attachment point  114  of external lever arm  108 . Spring  106  biases flapper  110  toward the closed positioned shown in  FIG. 1A . When in the fully closed position, flap  110  resides at an angle other than 90° to a plane extending normal to the longitudinal axis of conduit  102 . The angle of the flap with respect to a cross-sectional normal plane of conduit  102  is designated A. 
   In operation, exhaust pressure is incident on flap  110  from the left as viewed in  FIGS. 1A-4B . When the exhaust pressure is sufficient to overcome the bias force of spring  106 , the flap  110  will start to rotate about axle  112 . The torque on valve flap  110  is determined by the bias spring force multiplied by the distance d which is the distance d between the axis of the spring and axle  112 . The spring force increases as the valve flap opens and the spring  106  stretches. However, d gets shorter as the valve continues to open resulting in the torque approaching zero as the longitudinal axis of the spring approaches an “over-center” position—i.e., as it approaches intersection with a longitudinal axis of the axle  112 . This nearly over-center positioning of the valve flap as shown at  410  in  FIG. 4A  and  FIG. 4B  results in a substantially horizontal position of the flap when in the fully open position. This positioning, in turn, minimizes back pressure in the conduit when the valve is in the fully open position. Additionally, it is to be noted that the conduit itself supplies the stop mechanism for the valve flap in both its fully closed and fully opened positions. In the fully closed position, the arcuate edges of flap  114  contact the interior surface of conduit  102  to define that position. Conversely, when in the fully opened position, as shown in  FIGS. 4A and 4B , flap  410  utilizes its lateral linear edges ( 116  and  118  of  FIG. 1B ) to come into contact with the inner surface of conduit  402  to thereby provide a stop position for the fully opened position of flap  410 . 
   Rotating the valve flap such that the spring approaches the over-center condition also results in an easier maintenance of the valve in the fully opened position. 
     FIGS. 5A and 5B  show a first axle arrangement suitable for use with the valve assembly disclosed herein. Valve flap  510  rotates within conduit  502  about axle  512  which is placed asymmetrically with respect to the plane of flap  510 . A bias spring  506  extends between anchor point  504  and an attachment point  514  on lever arm  508 . As seen from  FIG. 5B , axle  512  which is journaled to conduit  502  via appropriate apertures, extends only so far at its leftmost end as shown in  FIG. 5B  so as to provide clearance between the axle  512  and spring  506 . With this clearance, the spring goes to near over-center and holds that position until the exhaust flow pressure is reduced significantly. At that point, the valve flap snaps to the closed position. Lever arm  508  protrudes from axle  512  either as a separately attachable element or as an integral protrusion of axle  512 . 
     FIGS. 6A and 6B  depict an alternative axle arrangement for use with the valve assembly disclosed. In this arrangement axle  612  extends outwardly of the conduit for a distance sufficient that it intersects the ultimate location of spring  606  when in its fully extended position. Hence, in this arrangement, spring  606  will contact axle  612  and wrap around it when the fully opened position is achieved. With this arrangement, since spring  606  wraps around axle  612 , the spring will pull the flap  610  to the closed position as soon as the exhaust flow pressure is reduced to a level unable to overcome the spring force. 
     FIG. 7  depicts one approach to achieving nearly full closure of the exhaust conduit by the disclosed valve assembly when the valve flap is put in its fully closed position. As seen from  FIG. 77  clearance areas such as  120  and  122  of  FIG. 1B  are substantially eliminated by flattening sides of conduit  700  such that it conforms more nearly to the overall peripheral shape of valve flap  710 . Section  724  and section  726  are flattened areas of conduit  700  to more nearly parallel the linear first and second edges of valve flap  710 . Of course it will be apparent to those skilled in the art that some clearance between the linear edges of valve flap  710  and conduit walls  724  and  726  must be present to prevent jamming of the valve flap upon rotating. 
   An exemplary application of the disclosed valve assembly is for an automotive exhaust system muffler, such as that shown in  FIG. 8 . 
   Muffler  800  has a housing comprised of a substantially cylindrical outer shell  818  closed at input and output ends by an input header  810  and an output header  812 . A partition  814  is attached to outer shell  818  at a position to define muffler chambers  824  and  826  on either side thereof. Partition  814  additionally includes at least one aperture  820 ,  822  enabling fluid communication between the chambers  824  and  826  inside muffler  800 . Optionally, sound absorbing material  816  may be placed in one or both interior muffler chambers. 
   Extending through muffler  800  by passing through input header  810 , partition  814  and output header  812  is a through pipe  802 . Pipe  802  includes a first plurality of perforations  806  enabling an input section of pipe  802  to have fluid communication with the muffler chamber  824  surrounding it. Pipe  802  has a second plurality of perforations  808  at an output end enabling fluid communication from the chamber  826  surrounding it to pipe  802 . 
   Positioned between the first and second set of perforations of pipe  802  is a valve assembly  100  arranged as previously described in conjunction with  FIGS. 1A-4B . Hence, in the closed position of valve assembly  100 , exhaust will enter muffler  800  at the input end  828  of pipe  802  as seen in  FIG. 8  and will flow through perforations  806  into the sound absorbing material  816  surrounding the pipe in chamber  824 . The exhaust then flows from the first chamber  824  to the second chamber  826  via apertures  820 ,  822  in partition  814 . Finally, the exhaust flows from the second chamber  826  through perforations  808  in through pipe  802  and out an exit end  830  of the pipe  802  as seen from  FIG. 8 . 
   When the exhaust pressure is high enough to overcome the force of bias spring  106 , the valve flap  110  will open to a nearly horizontal position within pipe  802  to essentially have most of the exhaust gas bypass the first and second chambers and their associated sound absorbing material. Since the flap  110  will be substantially horizontal in  FIG. 8  in the fully open position, back pressure in muffler  800  is minimized. 
   Another exemplary application of the disclosed valve assembly is for a first alternative automotive exhaust system muffler, such as that shown in  FIG. 9 . 
   Muffler  900  has a housing comprised of a substantially cylindrical outer shell  918  closed at input and output ends by an input header  910  and an output header  912 . A first partition  914   a  is attached to outer shell  918  at a position to define first muffler chamber  924  on a first side thereof. A second partition  914   b  is attached to outer shell  918  at a position to define a second muffler chamber  926  on a first side thereof. The second sides of partitions  914   a  and  914   b  define a third muffler chamber  932 . First partition  914   a  additionally includes at least one aperture  920   a ,  922   a  enabling fluid communication between the chambers  924  and  932  inside muffler  900 . Second partition  914   b  includes at least one aperture  920   b ,  922   b  enabling fluid communication between chambers  932  and  926 . Optionally, sound absorbing material  916  may be placed in one or both first and second muffler chambers. No sound absorbing material is placed in chamber  932 . 
   Extending through muffler  900  by passing through input header  910 , partitions  914   a  and  914   b  and output header  912  is a through pipe comprised of an input section  902  and an output section  904 . Pipe section  902  includes a first plurality of perforations  906  enabling an input section  902  to have fluid communication with the muffler chamber  924  surrounding it. Pipe section  904  has a second plurality of perforations  908  enabling fluid communication from the chamber  926  surrounding it to pipe section  904 . 
   Positioned between the first and second set of perforations of the through pipe  902 ,  904  in chamber  932  is a valve assembly  100  arranged as previously described in conjunctions with  FIGS. 1A-4B . Hence, in the closed position of valve assembly  100 , exhaust will enter muffler  900  at the input end  928  of pipe section  902  as seen in  FIG. 9  and will flow through perforations  906  into the sound absorbing material  916  surround the pipe in chamber  924 . The exhaust then flows from the first chamber  924  to the second chamber  926  through chamber  932  via apertures  920   a ,  922   a  in partition  914   a  and then via apertures  920   b ,  922   b  in partition  914   b . Finally, the exhaust flows from the second chamber  926  through perforations  908  in through pipe outlet section  904  and out an exit end  930  of the pipe section  904  as seen from  FIG. 9 . 
   When the exhaust pressure is high enough to overcome the force of bias spring  106 , the valve flap  110  will open to a nearly horizontal position within pipe  902 ,  904  to essentially have most of the exhaust gas bypass the first and second chambers  924 ,  926  and their associated sound absorbing material  916 . Since the flap  110  will be substantially horizontal in  FIG. 9  in the fully open position, back pressure in muffler  900  is minimized. 
   Since no sound absorbing material is placed in chamber  932 , there will be no interference between material  916  and those portions of valve assembly  100  located exteriorly of the through pipe  902 ,  904 . This, in turn, simplifies construction and placement of material  916  inside chambers  924  and  926  of muffler  900 . 
   Yet another exemplary application of the disclosed valve assembly is for a second alternative automotive exhaust system muffler, such as that shown in  FIG. 10 . Muffler  1000  uses a so-called side in-center out muffler style wherein at least one of the muffler inlet and the muffler outlet is displaced from a central longitudinal axis of the muffler housing. In all other respects, muffler  1000  of  FIG. 10  is substantially identical to muffler  900  of  FIG. 9 . It will be understood by those skilled in the art that the teachings herein are applicable also to mufflers having the inlet centered on the muffler axis and the outlet offset therefrom, or to mufflers having both the inlet and the outlet offset from the muffler longitudinal axis. 
   Muffler  1000  has a housing comprised of a substantially cylindrical outer shell  1018  closed at input and output ends by an input header  1010  and an output header  1012 . A first partition  1014   a  is attached to outer shell  1018  at a position to define muffler chamber  1024  on a first side thereof. A second partition  1014   b  is attached to outer shell  1018  at a position to define a second muffler chamber  1026  on a first side thereof. The second sides of partitions  1014   a ,  1014   b  define a third muffler chamber  1032 . First partition  1014   a  additionally includes at least one aperture at  1020   a ,  1022   a  enabling fluid communication between the chambers  1024  and  1032  inside muffler  1000 . Second partition  1014   b  includes at least one aperture  1020   b ,  1022   b  enabling fluid communication between chambers  1032  and  1026 . Optionally, sound absorbing material  1016  may be placed in one or both first and second interior muffler chambers. No such material is placed within chamber  1032 . 
   Extending though muffler  1000  by passing through input header  1010 , partitions  1014   a  and  1014   b  and output header  1012  is a through pipe comprised of an angular input section  1002  and a linear output section  1004 . Section  1002  includes a first plurality of perforations  1006  enabling input section  1002  to have fluid communication with the muffler chamber  1024  surrounding it. Pipe section  1004  has a second plurality of perforations  1008  enabling fluid communication from the chamber  1026  surrounding it to pipe section  1004 . 
   Positioned between the first and second set of perforations of the through pipe  1002 ,  1004  in chamber  1032  is a valve assembly  100  arranged as previously described in conjunction with  FIGS. 1A-4B . Hence, in the closed position of valve assembly  100 , exhaust will enter muffler  1000  at the input end  1028  of pipe section  1002  as seen in  FIG. 10  and will flow through perforations  1006  into the sound absorbing material  1016  surrounding the pipe in chamber  1024 . The exhaust then flows from the first chamber  1024  to the second chamber  1026  through chamber  1032  via apertures  1020   a ,  1022   a  in partition  1014   a  and then via apertures  1020   b ,  1022   b  in partition  1014   b . Finally, the exhaust flows from the second chamber  1026  through perforations  1008  in through pipe outlet section  1004  and out and exit end  1030  of the pipe section  1004  as seen from  FIG. 10 . 
   When the exhaust pressure is high enough to overcome the force of bias spring  106 , the valve flap  110  will open to a nearly horizontal position within pipe  1002 ,  1004  to essentially have most of the exhaust gas bypass the first and second chambers  1024 ,  1026  and their associated sound absorbing material  1016 . Since the flap  110  will be substantially horizontal in  FIG. 10  in the fully open position, back pressure in muffler  1000  is minimized. 
   Again, since no sound absorbing material is placed in chamber  1032 , there will be no interference between material  1016  and those portions of valve assembly  100  located exteriorly of through pipe  1002 ,  1004 . This offers the same advantages as set forth for muffler  900  of  FIG. 9 . 
   The invention has been described in conjunction with a detailed description of embodiments disclosed for the sake of example only. The scope and spirit of the invention are to be determined from an appropriate interpretation of the appended claims.