Abstract:
An exhaust pressure actuated valve assembly for placement inside a tubular exhaust conduit includes a valve plate rotatable between open and closed positions. An axle is adapted to pivotally couple the valve plate to the exhaust conduit about a longitudinal axis of the axle. The axle axis is adapted to extend in a direction substantially perpendicular to a direction of exhaust flow through the conduit. A cantilevered spring pad has a first portion coupled to the valve plate and a second portion spaced apart from the valve plate. The second portion is oriented to contact an inner surface of the conduit as the valve plate moves toward the closed position to dampen vibration.

Description:
FIELD 
     The present disclosure relates to a valve for an exhaust system. The valve includes a rotatable valve plate equipped with a vibration damping spring pad. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Many exhaust systems in the automotive field 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 an electric motor or a solenoid. Passive valves utilize the pressure of the exhaust stream in the conduit with which the valve is associated. 
     Either type of valve may be susceptible to problems of accelerated wear, vibratory noise, or chatter when a closing element such as a valve plate of the valve switches from an open position to a fully closed position and a portion of the valve plate contacts an inner surface of the conduit. Electric motors may be controlled to reduce the rate of valve plate movement as the plate approaches the conduit. This level of control is typically unavailable for passive valves that are loaded toward the closed position by a spring. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     An exhaust pressure actuated valve assembly for placement inside a tubular exhaust conduit includes a valve plate rotatable between open and closed positions. An axle is adapted to pivotally couple the valve plate to the exhaust conduit about a longitudinal axis of the axle. The axle axis is adapted to extend in a direction substantially perpendicular to a direction of exhaust flow through the conduit. A cantilevered spring pad has a first portion coupled to the valve plate and a second portion spaced apart from the valve plate. The second portion is oriented to contact an inner surface of the conduit as the valve plate moves toward the closed position to dampen vibration. 
     An exhaust pressure actuated valve assembly for placement inside a tubular exhaust conduit includes an axle extending through the conduit and a valve plate fixed to the axle and positioned in the conduit. The valve plate is rotatable between open and closed positions. A spring pad includes a first portion fixed to the valve plate and a second portion spaced apart from the valve plate such that the second portion is shaped as a cantilevered beam having one end fixed to the first portion and an opposite free distal end spaced apart from the valve plate. The spring pad is positioned to contact an inner surface of the conduit when the valve plate is in the closed position. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
       The objects and features of the present teachings will become apparent upon a reading of a 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 teachings of the present disclosure; 
         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; 
         FIG. 5  is a front plan view of a valve plate assembly arranged in accordance with the teachings of the present disclosure; 
         FIG. 6  is a side plan view of the valve plate assembly depicted in  FIG. 5 ; 
         FIG. 7  is a front plan view of an alternate valve plate assembly; 
         FIG. 8  is a cross-sectional view of the alternate valve plate assembly taken along line  8 - 8  shown in  FIG. 7 ; and 
         FIG. 9  is an exploded view of a spring pad and valve plate of the alternate plate assembly. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     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 plate  110 , a valve support shaft or axle  112  and a spring attachment  114  protruding from axle  112 . 
     Valve plate  110  has first and second arcuate edges  113 ,  115  substantially conforming to an interior arcuate surface of conduit  102 . Valve plate  110  additionally has linear side edges  116  and  118  which provide clearance  120 ,  122  between valve plate  110  and an interior surface of conduit  102  when the valve plate is in the closed position shown in  FIGS. 1A and 1B . Bias element or valve spring  106  extends between spring anchor  104  on conduit  102  and spring attachment  114  of external lever arm  108 . Spring  106  biases valve plate  110  toward the closed positioned shown in  FIG. 1A . When in the fully closed position, valve plate  110  resides at an angle other than 90° to a plane extending normal to the longitudinal axis of conduit  102 . The angle of valve plate  110  with respect to a cross-sectional normal plane of conduit  102  is designated A. 
     In operation, exhaust pressure is incident on valve plate  110  from the left as viewed in  FIGS. 1A-4B . When the exhaust pressure is sufficient to overcome the bias force of spring  106 , valve plate  110  will start to rotate about axle  112 . The torque on valve plate  110  is determined by the bias spring force multiplied by the distance d which is the distance d between the axis of the spring  106  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 spring  106  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 spring  106  results in a substantially horizontal position of valve plate  110  when in the fully open position as shown at  FIG. 4A  and  FIG. 4B . This positioning, in turn, minimizes back pressure in the conduit when the valve is in the fully open position. Rotating valve plate  110  that spring  106  approaches the over-center condition also results in an easier maintenance of valve plate  110  in the fully opened position. 
     As shown in  FIGS. 5 and 6 , valve plate  110  includes a first surface  160 , an opposite second surface  162  and an indentation  164  in the valve plate for receipt of axle  112 . Valve plate  110  and axle  112  are substantially similar to components of the snap action valve assembly disclosed in commonly assigned U.S. Pat. No. 7,434,570, herein incorporated by reference. An improvement to valve plate  110  is the addition of a cantilevered spring pad  152  having a first surface  156  and an opposite second surface  158 . Spring pad  152  is preferably comprised of a resilient vibration absorbing knitted metal mesh material such as 316 stainless steel, 430 stainless steel, or Inconel. 
     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, spring pad  152  and arcuate edge  115  of valve plate  110  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 , valve plate  110  utilizes its lateral linear edges ( 116  and  118  of  FIG. 1B ) to come into contact with the inner surface of conduit  102  to thereby provide a stop position for the fully opened position of valve plate  110 . 
     Spring pad  152  includes compressed regions  154   a  and  154   b  having an increased density to promote stronger spot welding of spring pad  152  to valve plate  110  in the area of compressed regions  154   a  and  154   b . Compressed regions  154   a  and  154   b  include substantially planar upper surfaces  155   a ,  155   b  having a circular perimeter, as shown. Compressed regions  154   a ,  154   b  define cylindrically-shaped pockets  157   a ,  157   b  inwardly extending from second surface  158 . 
     Axle  112  includes first and second portions extending from opposite edges of valve plate  110 . Each axle portion is surrounded by a bushing  168   a  and  168   b  which preferably also are comprised of knitted stainless steel mesh. 
     Spring pad  152  includes a first portion  180  including compressed regions  154   a ,  154   b  welded to valve plate  110 . First surface  156  of spring pad  152  contacts first surface  160  of valve plate  110  at first portion  180 . Spring pad  152  also includes a second or cantilevered portion  182  extending at a divergent angle to valve plate  110 . The divergent angle may range from 10 to 25 degrees. Spring pad  152  is shaped such that a peripheral edge  186  of spring pad  152  is substantially aligned with or slightly overhangs arcuate edge  113  of valve plate  110 . Spring pad  152  comes into contact with an inner surface of the conduit in which it is mounted when valve plate  110  swings toward its fully closed position as shown in solid lines in  FIGS. 1A and 1B . Spring pad  152  cushions the impact between valve plate  110  and conduit  102  as the valve plate is rotated to the fully closed position. The wire mesh spring pad  152  dampens vibrations and minimizes noise associated with moving valve plate  110  toward conduit  102 . 
     Cantilevered portion  182  of spring pad  152  includes a length “L”. For an exemplary snap-action valve positioned in a conduit having an inner diameter of approximately 2.0 inches, length L may be approximately 0.5 inches. For a valve positioned in a conduit having an inner diameter of approximately 3.25 inches, the length L may be 1.0 inches. It should be appreciated that length “L” may be increased to reduce the amount of force required to deflect cantilevered portion  182  toward valve plate  110 , thereby varying the spring rate of spring pad  152 . It is contemplated that a gap identified at “G” may be set to a distance ranging from 3-6 mm when spring pad  152  is in the free, or unloaded state. As valve plate  110  moves toward the fully closed position, cantilevered portion  182  will contact the inner surface of conduit  102  and deflect toward valve plate  110  to decelerate the valve plate. Spring pad  152  may act as a damper to minimize the noise emitted during a valve closing operation. 
     It is also within the scope of the present disclosure to vary the density of the wire mesh defining spring pad  152  to range from a mesh density of substantially 20% to a mesh density of 40%. As the mesh density is reduced, it is easier to deflect cantilevered portion  182  toward valve plate  110  for a given load. In addition, because the mesh density is less, the thickness of the spring pad is compressed a greater amount for a given load. As such, the damping characteristics of the valve may be tuned by selecting a desired mesh density. 
     The valve damping characteristics may be further optimized by modifying the mesh wire diameter used to construct spring pad  152 . It is contemplated that the mesh wire diameter may range from 0.06 mm to 0.15 mm. The thickness of the spring pad  152  may also be optimized to provide desirable damping characteristics. It is contemplated that a useful thickness range of spring pad  152  will lie between approximately 2.0 mm and 4.0 mm. It should be appreciated that spring pad  152  may reduce the sound emitted during a valve plate closing event through the use of cantilevered portion  182  deflecting under load as well as the wire mesh compressing under load. 
       FIGS. 7-9  depict an alternate valve assembly identified at reference numeral  200 . Valve  200  is substantially similar to valve  100 . As such, similar elements will be identified with like reference numerals increased by 100. As best depicted in  FIG. 9 , valve plate  210  includes a scalloped portion  211  sized and shaped to receive a rib or lip  213  of spring pad  252 . Rib  213  extends along a peripheral edge of spring pad  252 . Scalloped portion  211  remains clear of rib  213  should cantilevered portion  282  deflect to such an extent. Rib  213  increases the spring constant associated with deflecting cantilevered portion  282  toward valve plate  210 . Rib  213  also increases the structural rigidity of the spring pad  252  such that the spring pad maintains its intended shape during shipping and handling as well as after several opening and closing cycles of the valve. 
     It should be appreciated that both spring pad  152  and spring pad  252  are configured to include a gap between cantilevered portions  182 ,  282  and the respective valve plates  110 ,  210  in both a free state and a loaded state when the valve plate is in the closed position. When the valve plate moves from the closed position to the open position, cantilevered portion  182 ,  282  resiliently springs back to its initial position in the free and unloaded state. Similarly, the spring pad is only temporarily compressed to a reduced thickness when the valve plate is in a closed position. The spring pad resiliently returns to its initial thickness once the pad is no longer loaded into engagement with the interior surface of the conduit. Accordingly, the damping function of the spring pad will be useful at each valve plate closing event throughout the life of the valve. 
     The foregoing description has been provided for purposes of illustration and example. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.