Passive throttling valve outside of muffler

Abstract

An exhaust system includes an exhaust tube for conveying a heated exhaust flow from an engine. A valve is mounted at least partially within the exhaust tube for noise attenuation. The valve includes a bias member mounted outside of the engine exhaust tube within a heat transfer environment to maintain the bias member at a low temperature. The bias member biases the valve against the heat exhaust flow toward a predetermined position. The valve is mounted within a section of the tube having a smaller cross-sectional area and pivots into a larger cross-sectional area section of the exhaust tube to avoid interference with tube walls and provide a relatively large range of movement.

1 . An exhaust system comprising:
 an exhaust tube for conveying a heated exhaust flow;   a valve disposed at least partially within the exhaust tube; and   a bias member mounted outside of the exhaust tube, the bias member biasing the valve against the heated exhaust flow toward a predetermined position.   
   
   
       2 . The exhaust system as recited in  claim 1 , wherein the bias member is mounted within an ambient airflow heat transfer environment that removes heat from the bias member to maintain the bias member at a temperature below a threshold temperature. 
   
   
       3 . The exhaust system as recited in  claim 1 , wherein the valve includes a valve plate coupled to the bias member, and wherein the exhaust tube includes a tube wall having a slot therein, and the valve is mounted within the slot such that the valve plate is within the exhaust tube. 
   
   
       4 . The exhaust system as recited in  claim 1 , wherein the valve is moveable between a plurality of positions including the predetermined position, and the bias member comprises a spring rate that varies between the plurality of positions. 
   
   
       5 . The exhaust system as recited in  claim 1 , wherein the exhaust tube includes a first section having a first cross-sectional area adjacent a second section having a second cross-sectional area that is larger than the first cross-sectional area. 
   
   
       6 . The exhaust system as recited in  claim 5 , wherein the valve includes a valve plate that is mounted at least partially within the first section and is pivotable between a plurality of positions, and in at least one of the plurality of positions, the valve plate pivots into the second section. 
   
   
       7 . The exhaust system as recited in  claim 1 , wherein the valve includes a valve plate within the exhaust tube that is pivotable between a minimum flow position and a maximum flow position, wherein the valve plate permits the heated exhaust flow through the exhaust tube in each of the minimum flow position and the maximum flow position. 
   
   
       8 . The exhaust system as recited in  claim 1 , wherein the valve includes a valve plate within the exhaust tube that is pivotable about a pivot axis that is located at an outer perimeter of the valve plate. 
   
   
       9 . The exhaust system as recited in  claim 1 , wherein the valve includes a linkage connecting the valve and the bias member, the linkage comprising a first link having one end pivotally secured for rotation about a pivot axis of the valve, a second link having an end pivotally secured for rotation about a pivot axis of the bias member, and a third link that connects another end of the first link to another end of the second link. 
   
   
       10 . The exhaust system as recited in  claim 9 , wherein the first link comprises a first nominal length, and the second link comprises a second nominal length that is longer than the first nominal length. 
   
   
       11 . An exhaust system comprising:
 an exhaust tube for conveying a heated exhaust flow, the exhaust tube comprising a first section having a first cross-sectional area adjacent a second section having a second cross-sectional area that is larger than the first cross-sectional area;   a valve mounted at least partially within the first section, the valve operative to move between a plurality of positions in response to a force exerted on the valve from the heated exhaust flow, and wherein in one of the plurality of positions, the valve extends into the second section.   
   
   
       12 . The exhaust system as recited in  claim 11 , further comprising a bias member that biases the valve toward a predetermined position among the plurality of positions. 
   
   
       13 . The exhaust system as recited in  claim 12 , wherein the plurality of positions includes a minimum flow position where the valve is generally perpendicular to a direction of the heated exhaust gas flow through the exhaust tube, and a maximum flow position where the valve is oriented 90° relative to the valve in the minimum flow position. 
   
   
       14 . The exhaust system as recited in  claim 13 , wherein the predetermined position comprises the minimum flow position. 
   
   
       15 . The exhaust system as recited in  claim 12 , wherein the bias member comprises a spring having a spring rate that varies between the plurality of positions. 
   
   
       16 . The exhaust system as recited in  claim 11 , wherein the valve includes a pivot shaft having a pivot axis, and a valve plate coupled to the pivot shaft for movement about the pivot axis, wherein the valve plate is at least partially within the exhaust tube. 
   
   
       17 . The exhaust system as recited in  claim 16 , wherein the pivot shaft is entirely outside of the exhaust tube. 
   
   
       18 . A method of controlling a valve for use in an exhaust system, comprising the steps of:
 mounting the valve within a first section of an exhaust tube, the first section having a first cross-sectional area; and   moving the valve such that the valve extends at least partially into a second section of the exhaust tube having a second cross-sectional area that is larger than the first cross-sectional area to avoid interference between the valve and the second section.   
   
   
       19 . The method recited in  claim 18 , further including biasing the valve toward a predetermined position that is about perpendicular to a direction of an exhaust gas flow through the first section. 
   
   
       20 . The method recited in  claim 19 , further including passively moving the valve with a force provided by the exhaust flow to an orientation that is about 90° relative to the valve predetermined position such that the valve extends into the second section. 
   
   
       21 . The method recited in  claim 18 , further including mounting a bias member of the valve outside of the exhaust tube in an air flow to maintain a temperature of the bias member below a temperature of an exhaust gas flow through the exhaust tube.