Method and apparatus for regenerating an aftertreatment device for a spark-ignition direct-injection engine

Abstract

The disclosure sets forth operating a spark-ignition, direct-fuel injection internal combustion engine equipped with an exhaust aftertreatment system including a lean-NOx adsorber device. The engine is operated substantially un-throttled and at a lean air/fuel ratio and a first fuel pulse is injected to meet an engine output torque during a compression stroke of each engine cycle prior to a spark-ignition event. When regeneration of the lean-NOx adsorber device is commanded, a second fuel pulse is injected during a second engine stroke of each engine cycle.

1 . Method for controlling operation of a spark-ignition, direct-fuel injection internal combustion engine, comprising:
 equipping the engine with an exhaust aftertreatment system including a lean-NOx adsorber device;   operating the engine substantially un-throttled and at a lean air/fuel ratio;   injecting a first fuel pulse sufficient to power the engine to achieve an engine output torque during a compression stroke of each engine cycle prior to a spark-ignition event;   commanding a regeneration of the lean-NOx adsorber device; and   injecting a second fuel pulse during a second engine stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device.   
     
     
         2 . The method of  claim 1 , comprising injecting the second fuel pulse during an intake stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device. 
     
     
         3 . The method of  claim 2 , further comprising injecting a third fuel pulse during an expansion stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device. 
     
     
         4 . The method of  claim 3 , further comprising the first and third fuel pulses sufficient to power the engine to achieve the engine output torque. 
     
     
         5 . The method of  claim 3 , further comprising injecting a fourth fuel pulse during an exhaust stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device. 
     
     
         6 . The method of  claim 1 , comprising injecting the second fuel pulse during an exhaust stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device. 
     
     
         7 . The method of  claim 1 , comprising injecting the second fuel pulse during an expansion stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device. 
     
     
         8 . The method of  claim 1 , wherein the exhaust aftertreatment system includes a three-way catalytic converter upstream of the lean-NOx adsorber device. 
     
     
         9 . The method of  claim 8 , comprising injecting the second fuel pulse sufficient to generate an exhaust gas feedstream having a rich air/fuel ratio sufficient for a portion of exhaust gas reductants to break through the three-way catalytic converter upstream of the lean-NOx adsorber device. 
     
     
         10 . Method for operating a spark-ignition, direct-fuel injection internal combustion engine equipped with a lean-NOx adsorber device for exhaust gas aftertreatment, comprising:
 operating the engine in a stratified charge combustion mode including a first fuel pulse sufficient to power the engine to achieve an engine output torque;   commanding a regeneration of the lean-NOx adsorber device; and   continuing operating the engine in the stratified charge combustion mode and injecting a second fuel pulse during a second engine stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device, the second fuel pulse sufficient to generate an exhaust gas feedstream having a rich air/fuel ratio.   
     
     
         11 . The method of  claim 10 , wherein operating the engine in the stratified charge combustion mode comprises operating substantially un-throttled and injecting the first fuel pulse during a compression stroke of each engine cycle prior to a spark-ignition event. 
     
     
         12 . The method of  claim 11 , comprising injecting the second fuel pulse during an intake stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device. 
     
     
         13 . The method of  claim 12 , further comprising injecting a third fuel pulse during an expansion stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device. 
     
     
         14 . The method of  claim 13 , further comprising injecting a fourth fuel pulse during an exhaust stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device. 
     
     
         15 . The method of  claim 10 , comprising injecting the second fuel pulse during an exhaust stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device. 
     
     
         16 . The method of  claim 10 , comprising injecting the second fuel pulse during the expansion stroke of each engine cycle during the commanded regeneration of the lean-NOx adsorber device. 
     
     
         17 . The method of  claim 10 , wherein the exhaust aftertreatment system includes a three-way catalytic converter upstream of the lean-NOx adsorber device. 
     
     
         18 . The method of  claim 17 , comprising injecting the second fuel pulse sufficient to generate an exhaust gas feedstream having a rich air/fuel ratio sufficient for a portion of exhaust gas reductants to break through the three-way catalytic converter upstream of the lean-NOx adsorber device. 
     
     
         19 . Method for operating an internal combustion engine, comprising:
 equipping the engine with an exhaust aftertreatment system including a lean-NOx adsorber device;   operating the engine substantially un-throttled and at a lean air/fuel ratio;   directly injecting a first fuel pulse into a combustion chamber during a compression stroke of each engine cycle immediately prior to a spark-ignition event, wherein mass of fuel injected during the first fuel pulse is sufficient to power the engine to achieve an engine output torque; and   directly injecting a second fuel pulse during a second engine stroke of each engine cycle for a period of time, wherein mass of fuel injected during the second fuel pulse is determined based upon regenerating the lean-NOx adsorber device.   
     
     
         20 . The method of  claim 19 , comprising:
 directly injecting the first fuel pulse during the compression stroke to generate a stratified charge air/fuel distribution prior to initiating the spark-ignition event; and   directly injecting the second fuel pulse during the second engine stroke to generate a mixture of fuel and air in the exhaust gas feedstream that is uncombusted.   
     
     
         21 . The method of  claim 20 , further comprising directly injecting the second fuel pulse during the exhaust stroke and directly injecting a third fuel pulse during one of an intake stroke and the compression stroke to generate the uncombusted mixture of fuel and air in the exhaust gas feedstream.