Method of operating an internal combustion engine

Claim 1

An internal combustion engine including a turbocharger with a compressor and an exhaust gas turbine with a controllable gas admission flow guide structure, an air intake duct connected to said compressor for supplying combustion air to said engine, an exhaust pipe for discharging exhaust gas from said engine to said turbine, an exhaust gas recirculation pipe extending between said exhaust pipe and said air intake duct for recirculating exhaust gas from said exhaust pipe to said air intake duct, an exhaust gas recirculation valve arranged in said exhaust gas recirculation pipe for controlling the exhaust gas flow from said exhaust pipe to said air intake duct, an oxygen sensor arranged in said air intake duct downstream of the jointure of said exhaust gas recirculation pipe with said air intake duct, another oxygen sensor arranged in said exhaust pipe for sensing the oxygen content in said exhaust gas and a control unit to which said oxygen sensors are connected and which is connected to said exhaust gas recirculation valve and said turbine inlet flow guide structure for controlling said exhaust gas recirculation valve and said flow guide structure depending on the recirculation flow rate calculated from the sensor values provided by said oxygen sensors.

Claim 3

A method of operating on internal combustion engine including a turbocharger with a compressor and an exhaust gas turbine with a controllable gas admission flow guide structure, an air intake duct connected to said compressor for supplying combustion air to said engine, an exhaust pipe connected to said turbine for discharging exhaust gases from said engine to said turbine and an exhaust gas recirculation pipe extending between said exhaust pipe and said air intake duct for recirculating exhaust gas from said exhaust pipe to said combustion air intake duct and including an exhaust gas recirculation valve, said method comprising: sensing the oxygen content of the exhaust gas discharged from said engine, sensing the oxygen content of the combustion air supplied to said engine, determining from the oxygen content sensed in the exhaust gas and from the oxygen content sensed in the combustion air being supplied to said engine the instantaneous exhaust gas recirculation rate and controlling said exhaust gas recirculation valve and said flow guide structure depending on predetermined engine operating point-dependent exhaust gas recirculation rates.

Claim 4

A method of operating on internal combustion engine including a turbocharger with a compressor and an exhaust gas turbine with a controllable gas admission flow guide structure, an air intake duct connected to said compressor for supplying combustion air to said engine, an exhaust pipe connected to said turbine for discharging exhaust gases from said engine to said turbine and an exhaust gas recirculation pipe extending between said exhaust pipe and said air intake duct for recirculating exhaust gas from said exhaust pipe to said combustion air intake duct and including an exhaust gas recirculation valve, said method comprising: sensing the oxygen content of the exhaust gas discharged from said engine, sensing the oxygen content of the combustion air supplied to said engine, determining from the oxygen content sensed in the exhaust gas and from the oxygen content sensed in the combustion air being supplied to said engine the instantaneous exhaust gas recirculation rate and controlling said exhaust gas recirculation valve and said flow guide structure depending on predetermined engine operating point-dependent exhaust gas recirculation rates.