Exhaust system with cam-operated valve assembly and associated method

Abstract

An exhaust system for use with an engine comprises at least one valve and a camshaft. The at least one valve is configured to control flow in the exhaust system but is discrete from each intake valve of the engine and each exhaust valve of the engine. The camshaft is configured to operate the at least one valve. An associated method is disclosed.

1 . A method of operating an exhaust system associated with an engine, the method comprising the steps of: 
 rotating a camshaft of the exhaust system, and    operating at least one valve of the exhaust system in response to rotation of the camshaft so as to control flow in the exhaust system, the at least one valve being discrete from each intake valve of the engine and each exhaust valve of the engine.    
     
     
         2 . The method of  claim 1 , wherein: 
 the at least one valve comprises first and second valves, and    the operating step comprises operating the first and second valves in response to rotation of the camshaft, the first and second valves being discrete from each intake valve of the engine and each exhaust valve of the engine.    
     
     
         3 . The method of  claim 1 , wherein: 
 the at least one valve comprises an exhaust valve and an agent valve,    the operating step comprises (i) operating the exhaust valve in response to rotation of the camshaft so as to control flow of exhaust gas to an emissions trap, and (ii) operating the agent valve in response to rotation of the camshaft so as to control flow of regenerative agent to the emissions trap.    
     
     
         4 . The method of  claim 1 , wherein: 
 the at least one valve comprises first and second exhaust valves and first and second agent valves,    the operating step comprises (i) alternately opening and closing the first and second exhaust valves so as to alternate advancement of exhaust gas between first and second emission abatement devices in response to rotation of the camshaft, and (ii) alternately opening and closing the first and second agent valves so as to alternate advancement of regenerative agent between the first and second emission abatement devices in response to rotation of the camshaft.    
     
     
         5 . The method of  claim 1 , wherein: 
 the at least one valve comprises first and second valves,    the operating step comprises alternately opening and closing the first and second valves so as to alternate advancement of exhaust gas between first and second exhaust processors in response to rotation of the camshaft.    
     
     
         6 . The method of  claim 1 , further comprising the step of changing the number of operational engine cylinders of the engine from a non-zero first number to a non-zero second number, wherein: 
 the at least one valve comprises first and second exhaust valves,    the operating step comprises (i) opening the first valve with the camshaft so as to advance exhaust gas to a first sound abatement device in response to the changing step, and (ii) closing the second valve with the camshaft so as block advancement of exhaust gas to a second sound abatement device in response to the changing step.    
     
     
         7 . The method of  claim 1 , wherein the operating step comprises (i) at least partially closing the at least one valve with the camshaft so as to restrict exhaust gas flow in the exhaust system, and (ii) applying backpressure to the engine in response to the closing step.  
     
     
         8 . The method of  claim 1 , wherein the operating step comprises controlling flow of air with the at least one valve in response to rotation of the camshaft.  
     
     
         9 . The method of  claim 1 , wherein the operating step comprises controlling flow of a NOx reductant to an SCR catalyst with the at least one valve in response to rotation of the camshaft.  
     
     
         10 . An exhaust system for use with an engine, comprising: 
 at least one valve configured to control flow in the exhaust system, the at least one valve being discrete from each intake valve of the engine and each exhaust valve of the engine, and    a camshaft configured to operate the at least one valve.    
     
     
         11 . The exhaust system of  claim 10 , wherein: 
 the at least one valve comprises first and second valves, and    the camshaft is configured to operate both of the first and second valves.    
     
     
         12 . The exhaust system of  claim 11 , further comprising an upstream passageway and first and second downstream passageways, wherein: 
 the first valve is positioned fluidly between the upstream passageway and the first downstream passageway to control flow from the upstream passageway to the first downstream passageway in response to operation of the camshaft, and    the second valve is positioned fluidly between the upstream passageway and the second downstream passageway to control flow from the upstream passageway to the second downstream passageway in response to operation of the camshaft.    
     
     
         13 . The exhaust system of  claim 11 , further comprising first and second upstream passageways and a downstream passageway, wherein: 
 the first valve is positioned fluidly between the first upstream passageway and the downstream passageway to control flow from the first upstream passageway to the downstream passageway in response to operation of the camshaft, and    the second valve is positioned fluidly between the second upstream passageway and the downstream passageway to control flow from the second upstream passageway to the downstream passageway in response to operation of the camshaft.    
     
     
         14 . The exhaust system of  claim 11 , further comprising a cylinder deactivation unit, a shaft rotator secured to the camshaft to rotate the camshaft, and first and second sound abatement devices, wherein: 
 the first valve is configured to control flow of exhaust gas to the first sound abatement device,    the second valve is configured to control flow of exhaust gas to the second sound abatement device, and    the cylinder deactivation unit is configured to operate the shaft rotator in response to a change in the number of operational engine cylinders of the engine from a non-zero first number to a non-zero second number.    
     
     
         15 . The exhaust system of  claim 11 , further comprising first and second emission abatement devices, a regenerative agent supplier configured to supply regenerative agent for use in regeneration of the first and second emission abatement devices, wherein: 
 the first valve is configured to control flow of exhaust gas of the engine to the first emission abatement device,    the second valve is configured to control flow of exhaust gas of the engine to the second emission abatement device,    the at least one valve comprises a third valve configured to control flow of regenerative agent from the regenerative agent supplier to the first emission abatement device and a fourth valve configured to control flow of regenerative agent from the regenerative agent supplier to the second emission abatement device, and    the camshaft is configured to control operation of the first, second, third, and fourth valves.    
     
     
         16 . The exhaust system of  claim 10 , further comprising a block defining a port in which the at least one valve extends, wherein a portion of the at least one valve and the camshaft are positioned on the same side of the block.  
     
     
         17 . The exhaust system of  claim 16 , further comprising a cover covering the portion of the at least one valve and the camshaft.  
     
     
         18 . The exhaust system of  claim 10 , further comprising a NOx reductant supplier and an SCR catalyst, wherein the at least one valve is positioned fluidly between the NOx reductant supplier and the SCR catalyst to control flow of NOx reductant from the NOx reductant supplier to the SCR catalyst in response to operation of the camshaft.  
     
     
         19 . The exhaust system of  claim 10 , further comprising an air supplier, wherein the at least one valve is fluidly coupled to the air supplier to control introduction of air into the exhaust system in response to operation of the camshaft.  
     
     
         20 . An exhaust system, comprising: 
 first and second NOx traps,    first and second exhaust valves, the first exhaust valve for controlling flow of exhaust gas to the first NOx trap, the second exhaust valve for controlling flow of exhaust gas to the second NOx trap,    first and second reductant valves, the first reductant valve for controlling flow of NOx reductant to the first NOx trap, the second reductant valve for controlling flow of NOx reductant to the second NOx trap, and    a camshaft for controlling operation of the first and second exhaust valves and the first and second reductant valves.