Various methods and systems are provided for controlling emissions. In one example, a controller is configured to respond to a sensed exhaust oxygen concentration by changing a fuel injection timing to maintain particulate matter (PM) within a range, and then adjusting an exhaust gas recirculation (EGR) amount based on NOx sensor output and based on the change in fuel injection timing.

Various methods and systems are provided for controlling emissions. In one example, a controller is configured to respond to a sensed exhaust oxygen concentration by changing a fuel injection timing to maintain particulate matter (PM) within a range, and then adjusting an exhaust gas recirculation (EGR) amount based on NOx sensor output and based on the change in fuel injection timing.

Various methods and systems are provided for controlling emissions. In one example, a controller is configured to respond to a sensed exhaust oxygen concentration by changing a fuel injection timing to maintain particulate matter (PM) within a range, and then adjusting an exhaust gas recirculation (EGR) amount based on NOx sensor output and based on the change in fuel injection timing.

A control arithmetic unit uses a control storage area to compute a target control amount for combustion of an internal combustion engine according to a user required torque. A monitoring arithmetic unit uses a monitoring storage area to perform computation and to monitor presence or absence of a torque anomaly state in which an estimated torque is deviated from an engine required torque by a predetermined amount or more. The monitoring arithmetic unit computes the estimated torque by using a blow through state amount. The blow through state amount is a quantity of intake air blowing through out of an exhaust port in an intake stroke of the internal combustion engine, a degree to which intake air blows through out of the exhaust port, or an in-cylinder air quantity which is a quantity of air filled into a combustion chamber of the internal combustion engine.

A control arithmetic unit uses a control storage area to compute a target control amount for combustion of an internal combustion engine according to a user required torque. A monitoring arithmetic unit uses a monitoring storage area to perform computation and to monitor presence or absence of a torque anomaly state in which an estimated torque is deviated from an engine required torque by a predetermined amount or more. The monitoring arithmetic unit computes the estimated torque by using a blow through state amount. The blow through state amount is a quantity of intake air blowing through out of an exhaust port in an intake stroke of the internal combustion engine, a degree to which intake air blows through out of the exhaust port, or an in-cylinder air quantity which is a quantity of air filled into a combustion chamber of the internal combustion engine.

Various methods and systems are provided for controlling emissions. In one example, a controller is configured to respond to a sensed exhaust oxygen concentration by changing a fuel injection timing to maintain particulate matter (PM) within a range, and then adjusting an exhaust gas recirculation (EGR) amount based on NOx sensor output and based on the change in fuel injection timing.

An air-fuel ratio region detection unit, including a first determination voltage higher than a target voltage value indicating the stoichiometric air-fuel ratio, and a second determination voltage lower than the target voltage value, determines that an air-fuel ratio of an engine is within a first rich region when an oxygen sensor output equals or exceeds the first determination voltage, determines that the air-fuel ratio is within a second rich region when the oxygen sensor output equals or exceeds the target voltage value but is lower than the first determination voltage, determines that the air-fuel ratio is within a second lean region when the oxygen sensor output equals or exceeds the second determination voltage but is lower than the target voltage value, and determines that the air-fuel ratio is within a first lean region when the oxygen sensor output is lower than the second determination voltage.

An air-fuel ratio region detection unit, including a first determination voltage higher than a target voltage value indicating the stoichiometric air-fuel ratio, and a second determination voltage lower than the target voltage value, determines that an air-fuel ratio of an engine is within a first rich region when an oxygen sensor output equals or exceeds the first determination voltage, determines that the air-fuel ratio is within a second rich region when the oxygen sensor output equals or exceeds the target voltage value but is lower than the first determination voltage, determines that the air-fuel ratio is within a second lean region when the oxygen sensor output equals or exceeds the second determination voltage but is lower than the target voltage value, and determines that the air-fuel ratio is within a first lean region when the oxygen sensor output is lower than the second determination voltage.