Passive valve assembly for vehicle exhaust system

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 is movable between a fully closed position where a maximum portion of the exhaust gas flow path is blocked by the vane and a fully open position where a minimum portion of the exhaust gas flow path is blocked by the vane. The closed position comprises a start position for the passive valve assembly when there is no exhaust gas flow. The vane is obliquely orientated to a plane that is perpendicular to a centerline of the exhaust component when the vane is in the start position.

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 a non-vertical start position relative to exhaust gas flow to reduce valve flutter.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. ...

AI Technical Summary

Benefits of technology

[0014]This configuration provides a non-bypass exhaust gas flow path that is 80%-97% blocked when the vane is in the closed position in combination with providing a rapid open area change with only a small angle change a

Problems solved by technology

Although effective, these components are often relatively large in size and provide limited nose attenuation.

Increasing muffler volume is disadvantageous from a cost, material, and packaging space perspective.

Increasing backpressure can adversely affect engine power.

Passive valves installed within mufflers are subjected to high temperatures, which limit the passive valve's effectiveness from material and cost perspectives.

By-pass configurations are disadvantageous from material cost and packaging perspectives.

Also, the inclusion of the passive valve assembly within the exhaust system presents additional noise challenges, which must be addressed.

One disadvantage with this traditional orientation is that valve flutter is generated with pressure fluctuation as the vane starts to move from the closed position toward the open position.

As such, these pressure fluctuations, i.e. small increases and decreases in gas flow pressures at lower engine operating speeds, can cause the vane to accordingly pivot back and forth (flutter) resulting in a generation of undesirable noise referred to as “chatter.”

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