Abstract:
A passive valve assembly for a vehicle exhaust system includes an exhaust component that defines an exhaust gas flow path and a vane that is positioned within the exhaust gas flow path. The vane has an elongated body structure that has a greater height than width. The vane is positioned to provide a high percentage of coverage when closed but is able to pivot to a fully horizontal position when open to allow maximum flow.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to provisional application No. 60/989,508 filed on Nov. 21, 2007. 
     
    
     TECHNICAL FIELD 
       [0002]    The subject invention relates to a passive valve assembly in a vehicle exhaust system, and more particularly to a passive valve assembly that has an elongated vane to improve valve performance. 
       BACKGROUND OF THE INVENTION 
       [0003]    Exhaust systems are widely known and used with combustion engines. Typically, an exhaust system includes exhaust tubes that convey hot exhaust gases from the engine to other exhaust system components, such as mufflers, resonators, etc. Mufflers and resonators include acoustic chambers that cancel out sound waves carried by the exhaust gases. Although effective, these components are often relatively large in size and provide limited nose attenuation. 
         [0004]    Attempts have been made to improve low frequency noise attenuation by either increasing muffler volume or increasing backpressure. Increasing muffler volume is disadvantageous from a cost, material, and packaging space perspective. Increasing backpressure can adversely affect engine power. 
         [0005]    Another solution for reducing low frequency noise is to use a passive valve assembly. Passive valve assemblies are either installed within a muffler, or are installed in a by-pass pipe configuration. Both of these known arrangements have certain disadvantages. Passive valves installed within mufflers are subjected to high temperatures, which limit the passive valve&#39;s effectiveness from material and cost perspectives. By-pass configurations are also disadvantageous from material cost and packaging perspectives. 
         [0006]    Further, when the passive valve is used in a by-pass pipe configuration, challenges are presented when the passive valve is moved toward a fully open position. The passive valve includes a flapper valve body or vane that is positioned within the exhaust pipe, with the vane being pivotable between open and closed positions. The passive valve is spring biased toward the closed position, and when exhaust gas pressure is sufficient to overcome this spring bias, the vane is pivoted toward the open position. In by-pass configurations, the vane provides 100% coverage, i.e. complete blockage, of the exhaust component when in the closed position. When closed, exhaust gases can flow outside of the exhaust pipe that houses the vane via a by-pass pipe that is connected to the exhaust pipe at locations upstream and downstream of the vane. 
         [0007]    When the vane is moved toward the fully open position potential interference challenges are presented by the shape of the pipe itself. Traditionally, the vane has been supported by a shaft mounted to a wall of the pipe, with the shaft defining a pivot axis of rotation. The pipe typically includes a curved pipe wall having an inner surface that defines the exhaust gas flow path. Due to the pivot axis of rotation being mounted close to the wall surface of the pipe, when the vane is pivoted, interference between the pipe and the vane can limit opening of the valve assembly. Limiting the opening angle is disadvantageous from a back pressure standpoint, in addition to failing to achieve a true fully open position for maximum flow. 
         [0008]    Therefore, there is a need to provide a passive valve arrangement for a non-bypass configuration that can minimize the effect of the open angle limit to achieve minimum backpressure penalties. This invention addresses those needs while avoiding the shortcomings and drawbacks of the prior art. 
       SUMMARY OF THE INVENTION 
       [0009]    A passive valve assembly for a vehicle exhaust system includes a vane having an elongated body structure. The elongated body structure has a greater height dimension than width dimension. 
         [0010]    In one example, the elongated body structure comprises a generally oval-shaped disc. The oval-shaped disc comprises a curved upper edge, a curved lower edge, and a pair of opposing straight side edges that extend between the curved upper edge and the curved lower edge. 
         [0011]    In one example, the elongated body structure includes a first portion to be coupled to a pivotable shaft. The elongated body structure extends from the first portion to a distal tip. The maximum vertical height dimension is defined by a line that extends from the first portion to the distal tip. 
         [0012]    The vane is pivotable between a closed position where a maximum portion of the exhaust gas flow path is blocked by the vane and an open position where a minimum portion of the exhaust gas flow path is blocked by the vane. The closed position also defines a start position for the vane when there is no exhaust gas flow, or minimal exhaust gas flow. In one example, the exhaust gas flow path is 90%-97% blocked when the vane is in the start/closed position. Further, in one example configuration, the vane is positioned at a 20 degree start angle to provide a more rapid open area change. In this configuration, due to the elongated shape of the vane, the vane can be pivoted through a range of 20 to 90 degrees without interfering with walls of the exhaust component. 
         [0013]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  shows a perspective view of one example of an exhaust component and passive valve assembly. 
           [0015]      FIG. 2  shows a side view of an exhaust component with a stop for a vane. 
           [0016]      FIG. 3  is a graph that shows blockage of an exhaust gas flow path vs. opening angle of the vane. 
           [0017]      FIG. 4  is a schematic view of the exhaust component and passive valve assembly of  FIG. 1  within an exhaust system. 
           [0018]      FIG. 5  is a schematic end view of the exhaust component with the passive valve assembly being in a closed position. 
           [0019]      FIG. 6  is a view similar to  FIG. 5  but showing the passive valve assembly in an open position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    As shown in  FIG. 1 , an exhaust component, such as an exhaust tube or pipe  10  includes an exhaust throttling valve, referred to as a passive valve assembly  12 . The passive valve assembly  12  is movable between an open position where there is minimal blockage of an exhaust gas flow path  16  and a closed position where a substantial portion of the exhaust gas flow path  16  is blocked. The passive valve assembly  12  is resiliently biased toward the closed position and is moved toward the open position when exhaust gas flow generates a pressure sufficient enough to overcome the biasing force. 
         [0021]    In the example shown, the exhaust pipe  10  comprises a single pipe body  14  that defines the exhaust gas flow path  16 . In one example, the pipe body  14  includes a curved outer surface  14   a  and a curved inner surface  14   b  that defines the exhaust gas flow path  16 . In one example, the pipe body  14  has a circular cross-section. 
         [0022]    The passive valve assembly  12  includes a valve body or vane  18  that blocks a portion of the exhaust gas flow path  16  when in the closed position. As discussed above, the vane  18  is pivoted toward the open position to minimize blockage of the exhaust gas flow path  16  in response to pressure exerted against the vane  18  by exhaust gases. 
         [0023]    In one example, the vane  18  is fixed to a shaft  20  with a connecting arm, shown schematically at  22  in  FIG. 1 . A slot  24  is formed within the curved outer surface  14   a  of the pipe body  14 . A housing  26 , shown in this example as a square metal structure, is received within this slot  24  and is welded to the pipe body  14 . Other housing configurations could also be used. The shaft  20  is rotatably supported within the housing  26  by first  28  and second  30  bushings or bearings and defines an axis of rotation A. 
         [0024]    The first bushing  28  is positioned generally at a first shaft end  32 . The first bushing  28  comprises a sealed interface for the first shaft end  32 . The shaft  20  includes a shaft body  34  that has a first collar  36  and a second collar  38 . The first bushing  28  includes a first bore that receives the first shaft end  32  such that the first collar  36  abuts directly against an end face of the first bushing  28  to provide a sealed interface. As such, exhaust gases cannot leak out of the first bushing  28  along a path between the shaft  20  and first bushing  28 . 
         [0025]    The second bushing  30  includes a second bore through which the shaft body  34  extends to a second shaft end  40 . The second collar  38  is located axially inboard of the second bushing  30 . The shaft  20  extends through the second bore to an axially outboard position relative to the second bushing  30 . A resilient member, such as a spring  42  for example, is coupled to the second shaft end  40  with a spring retainer  44 . The spring retainer  44  includes a first retainer piece  46  that is fixed to the housing  26  and a second retainer piece  48  that is fixed to the second shaft end  40 . One spring end  50  is associated with housing  26  via the first retainer piece  46  and a second spring end (not viewable in  FIG. 1  due to the spring retainer  44 ) is associated with the shaft  20  via the second retainer piece  48 . 
         [0026]    The vane  18  comprises a body structure  60 , such as a disc-shaped body for example, which includes a first portion  62  that is coupled to the shaft  20  with the connecting arm  22 . The body structure  60  extends from the first portion  62  to a second portion that comprises a distal tip  64 . As such, the tip  64  comprises a portion of the body structure  60  that is furthest from the axis of rotation A. 
         [0027]    A stop  66  is supported by the pipe body  14  and is positioned within the exhaust gas flow path  16 . The stop  66  defines the starting/closed position for the vane  18 . The tip  64  of the vane  18  engages the stop  66  when the spring  42  returns the vane  18  from the open position to the closed position. 
         [0028]    In one example, as shown in  FIGS. 1 and 2 , the stop  66  comprises a ramped surface  68  that begins at the inner surface  14   b  at a position upstream from the vane  18  and extends outwardly away from the inner surface  14   b  and toward the vane  18 . The ramped surface  68  then transitions into a stopper end surface  70  that extends back towards the inner surface  14   b . The tip  64  of the vane  18  engages the stopper end surface  70  when in the closed position. This also defines the starting position for the vane  18  when there is no exhaust gas flow, or only a minimal amount of exhaust gas flow that is not sufficient to overcome the biasing force of the resilient member. 
         [0029]    As shown in  FIG. 2 , the ramped surface  68  and the stopper end surface  70  are angled relative to the inner surface  14   b  of the pipe body  14 . The pipe body  14  defines a pipe centerline C, which is shown in  FIG. 2 . The ramped surface  68  is positioned at a ramp angle that is within a range of 10 to 45 degrees relative to the pipe centerline C. Similarly, the stopper end surface  70  is positioned at an angle relative to the pipe centerline C to define the start position. This will be discussed in greater detail below. In one example, the ramped surface  68  and the stopper end surface  70  are obliquely orientated relative to the inner surface  14   b  of the pipe  10  and relative to the pipe centerline C. 
         [0030]    In one example, a pad  72  is supported on the stopper end surface  70  to provide a cushioned surface to engage the tip  64  of the vane  18 . The pad  72  can be made from a mesh material or other similar material, for example, and can be attached to the stopper end surface  70  with any type of attachment method suitable for use within an exhaust component. 
         [0031]    The stop  66  is positioned at the tip  64  of the vane  18  to minimize closing forces. By positioning these contact surfaces as far as possible from the axis of rotation A, contact forces are reduced, which in turn increases durability. Further, the upstream ramped surface  68  of the stop  66  reduces backpressure, turbulence, and the generation of additional flow noise. 
         [0032]    The vane  18  is positioned to provide an exhaust gas flow path that is 80%-97% blocked when the vane  18  is in the start/closed position, as well as being positioned to provide a rapid open area change with only a small angle change at initial vane lift-off from the start/stop position. The vane  18  is movable between a fully closed position where a maximum portion of the exhaust gas flow path  16  is blocked by the vane  18  and a fully open position where a minimum portion of the exhaust gas flow path  16  is blocked by the vane  18 . As discussed above, the closed position also corresponds to the start position for the passive valve assembly when there is no, or low, exhaust gas flow. In this start position, the vane  18  is orientated to be non-perpendicular to a direction of the exhaust gas flow, which is indicated at  80  in  FIG. 2 . 
         [0033]    As discussed above, the pipe body  14  defines a pipe centerline C that extends along a length of the exhaust pipe  10 . The vane  18  is obliquely orientated relative to a plane P that is perpendicular to the pipe centerline C at the valve position in the exhaust gas flow path  16 . As shown in  FIG. 2 , the vane  18  is orientated at an angle {acute over (α)} relative to the plane P that is within a range of 10 to 35 degrees. This angle {acute over (α)} is defined by the angle of the stopper end surface  70 . 
         [0034]    As shown in  FIG. 3 , orientating the vane  18  in such a manner provides significant operational advantages in additional to improving noise reduction. Small opening angle changes provide rapid increases in open area, i.e. blockage of the exhaust gas flow path  16  quickly decreases with only very small changes in the opening angle. This significantly reduces flutter behavior, which has been associated with a rate of change of open area from a start position. 
         [0035]    In one example, shown in  FIG. 4 , the passive valve assembly  12  is positioned within an exhaust component  82 . In this example, the exhaust component  82  comprises a pipe that has a first end  84  coupled to a first exhaust component  86  and a second end  88  coupled to a second exhaust component  90 . The pipe comprises a non-bypass configuration with the pipe defining a sole exhaust gas flow path  92  between the first  86  and the second  90  exhaust components. A direction of exhaust gas flow is indicated by arrows  94 . As such, the passive valve assembly  12  comprises the only valve assembly that is positioned in the gas flow path  92  between the first  86  and second  90  exhaust components. 
         [0036]    In this configuration, as discussed above, the vane  18  is only pivoted from the start/closed position toward the open position in response to an exhaust gas flow  94  that exceeds a biasing force of the resilient member. As shown, the stop  66  is positioned to hold the vane  18  at the oblique starting angle. The resilient member returns the vane  18  into abutting engagement with the stop  66  when the exhaust gas flow is less than the biasing force of the resilient member. 
         [0037]    Further, the vane  18  is uniquely configured to provide pivoting capability to a fully horizontal open position without interference with the curved inner surface  14   b  of the pipe  10 . As shown in  FIG. 5 , the vane  18  has an elongated body structure  100  that is defined by a maximum vertical height dimension H and a maximum horizontal width dimension W that is perpendicular to the maximum vertical height dimension H. The elongated body structure  100  has a greater maximum vertical height dimension H than maximum horizontal width dimension W. 
         [0038]    The elongated body structure  100  has a generally oval-shape and includes a curved upper edge  102 , a curved lower edge  104 , and a pair of opposing straight side edges  106  that extend between the curved upper edge  102  and the curved lower edge  104 . In this configuration, the straight side edges  106  are orientated to be perpendicular to the axis of rotation A but do not intersect the axis of rotation A. This is due to the use of the connecting arm  22  to couple the vane  18  to the shaft  20 . 
         [0039]    As discussed above, the elongated body structure  100  of the vane includes the first portion  62  that is coupled to the shaft  20  with the connecting arm  22 . This first portion  62  extends to the distal tip  64  that engages the stop  66 . The maximum vertical height dimension H is defined by a line that extends from the first portion  62  to the distal tip  64 . As such, the maximum vertical height dimension H has a component that is generally perpendicular to a direction of the exhaust gas flow. 
         [0040]    As discussed above, the vane  18  is pivotable between a closed position where a maximum portion of the exhaust gas flow path is blocked by the vane  18  and an open position where a minimum portion of the exhaust gas flow path is blocked by the vane  18 . The fully closed position is shown in  FIG. 5  and the fully open position is shown in  FIG. 6 . The exhaust gas flow path is 80%-97% blocked when the vane  18  is in the closed position. 
         [0041]    In one example, the exhaust gas flow path is at least 90% blocked, and the start angle for the vane  18  (defined by the stopper end surface  70  as described above) is at least 20 degrees. In this configuration the vane  18  is easily pivotable from the start angle of 20 degree to a 90 degree angle relative to the plane P to achieve a fully horizontal open position as shown in  FIG. 6 . Due to the elongated shape of the vane  18  with the straight side edges  106 , this pivoting occurs without any interference from the curved inner surface  14   b  of the pipe  10 . Further, when the vane  18  is at this 90 degree position, it provides the least amount of blockage to maximize exhaust gas flow. 
         [0042]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.