Piston-type internal combustion engine

Abstract

A piston-type internal combustion engine ( 10 ) having an intake line ( 20 ) for delivering air to combustion chambers of the engine and an exhaust system ( 15, 22 ) for removing exhaust gases from said combustion chambers. The exhaust system includes equipment ( 29, 30 ) for reducing environmentally harmful exhaust emissions from the engine, which is intended to function with variable load in order to propel a vehicle. The exhaust system ( 15, 22 ) has a branch pipe ( 26 ) controlled by a valve ( 24 ) and bypassing at least one part of the equipment ( 29, 30 ) for reducing environmentally harmful exhaust emissions. The valve ( 24 ) is controlled so that it leads the exhaust gas flow through the branch pipe ( 26 ) over a part of the overall load range of the engine. The engine is optimized in order to give acceptable exhaust emissions over said part of the overall load range of the engine.

1 . A piston-type internal combustion engine ( 10 ) comprising: 
 an intake line ( 20 ) configured to deliver air to combustion chambers of the engine ( 10 ) and an exhaust system ( 15 ,  22 ) configured to remove exhaust gases from said combustion chambers, said exhaust system comprising equipment ( 29 ,  30 ) for reducing environmentally harmful exhaust emissions from the engine and which functions with variable load in order to propel a vehicle; and    said exhaust system ( 15 ,  22 ) comprises a branch pipe ( 26 ) controlled by a valve ( 24 ) and bypassing at least one part of said equipment ( 29 ,  30 ) that reduces environmentally harmful exhaust emissions, said valve ( 24 ) being controlled to lead the exhaust gas flow through the branch pipe ( 26 ) over a part of the overall load range of the engine and the engine is optimized in order to give acceptable exhaust emissions over said part of the overall load range of the engine.    
   
   
       2 . The internal combustion engine as recited in  claim 1 , wherein said part of the overall load range of the engine primarily comprises the low engine load range.  
   
   
       3 . The internal combustion engine as recited in  claim 1 , wherein said branch pipe ( 26 ) is coupled in parallel with a NO x  trap ( 30 ) for reducing nitrogen oxide emissions from the engine, and that an injector ( 29 ) for adding a combustible substance to the exhaust gases is located between the valve ( 24 ) and the NO x  trap ( 30 ), the substance permitting regeneration of said trap.  
   
   
       4 . The internal combustion engine as recited in  claim 1 , wherein said branch pipe ( 26 ) is coupled in parallel with an exhaust gas after-treatment system which comprises an SCR catalytic converter ( 30 ).  
   
   
       5 . The internal combustion engine as recited in  claim 1 , further comprising a regeneratable particle filter ( 23 ) located upstream of the valve ( 24 ), regeneration being possible whilst the exhaust gas flow is being led through the branch pipe ( 26 ).  
   
   
       6 . The internal combustion engine as recited in  claim 1 , wherein said branch pipe ( 26 ) is coupled in parallel with an exhaust gas after-treatment system which comprises an LNC catalytic converter ( 30 ).  
   
   
       7 . The internal combustion engine as recited in  claim 6 , further comprising a regeneratable particle filter ( 23 ) located downstream of a point ( 27 ) at which the branch pipe ( 26 ) and the LNC catalytic converter ( 30 ) containing the exhaust line converge and thereby permitting regeneration of the particle filter while the exhaust gas flow is being led via the branch pipe ( 26 ).  
   
   
       8 . The internal combustion engine as recited in  claim 6 , further comprising a desulfurization device ( 34 ) located upstream of the valve ( 24 ).  
   
   
       9 . The internal combustion engine as recited in  claim 1 , further comprising a system ( 31 - 33 ) configured to return cooled exhaust gases to the intake side of the engine in order to reduce the combustion temperature.