Apparatus and method for controlling an internal combustion engine

A control device for an internal combustion engine, the internal combustion engine including an exhaust gas control apparatus, an exhaust port, an intake port, an exhaust valve and an intake valve, the exhaust gas control apparatus configured to store NOx in exhaust gas under a leaner atmosphere with excessive oxygen compared to an atmosphere under a stoichiometric air-fuel ratio and the exhaust gas control apparatus configured to react, directly or indirectly, NOx with a reduction agent supplied from an upstream side of an exhaust flow to reduce NOx, the control device comprising:

• an electronic control unit configured to:
• (i) execute a rich spike control, the rich spike control being a control executed to temporarily change an in-cylinder air-fuel ratio from a leaner air-fuel ratio than the stoichiometric air-fuel ratio to the stoichiometric air-fuel ratio or a richer air-fuel ratio than the stoichiometric air-fuel ratio;
• (ii) vary an overlap amount of the intake valve and the exhaust valve such that the overlap amount is less during execution of the rich spike control than during non-execution of the rich spike control, in an operation range where a pressure of the intake port becomes higher than a pressure of the exhaust port;
• and
• (iii) decrease the overlap amount of the intake valve and the exhaust valve when the rich spike control is executed in the operation range where the pressure of the intake port becomes higher than the pressure of the exhaust port, wherein the overlap amount of the intake valve and the exhaust valve when the rich spike control is executed in the operation range where the pressure of the intake port is higher than the pressure of the exhaust port is less than or equal to the overlap amount of the intake valve and the exhaust valve when the rich spike control is executed in an operation range where the pressure of the intake port becomes less than or equal to the pressure of the exhaust port.