Patent ID: 7591130

Claim:
A method of controlling an internal combustion engine that causes a first emission and a second emission to be generated upon combustion of a fuel, wherein an amount of the second emission in an exhaust gas increases as an operating state of the engine is changed so as to reduce an amount of the first emission in the exhaust gas, and wherein an emission control device is provided in an exhaust passage so as to purify an exhaust gas by reducing at least one of the first emission and the second emission, comprising the steps of: determining a removal capability of the first emission and a removal capability of the second emission, respectively, in which the emission control device reduces an amount of one of the first emission and the second emission at predetermined constant intervals after rich spike or a recovery process of a filter is executed; and changing an operating state of the internal combustion engine, based on a ratio of the determined removal capabilities of the first emission to the determined removal capabilities of the second emission, so as to increase an amount of one emission of the first emission and the second emission for which the emission control device exhibits extra removal capability, relative to the amount of the other emission of the first emission and the second emission from the internal combustion engine, and so as to reduce an amount of the other emission for which the emission control device does not exhibit extra removal capability, relative to the amount of the one emission from the internal combustion engine, wherein the operating state of the internal combustion engine is set to a point on an equi-output line for the internal combustion engine, wherein the equi-output line is defined by engine speed of the internal combustion engine and torque of the internal combustion engine.