US Patent 7360356 Exhaust gas purifying apparatus for internal combustion engine

A main control computer commands a second sub-control computer to perform a reduced-cylinder operation when the coolant temperature detected by a coolant temperature sensor is greater than or equal to a reference temperature, and the exhaust temperature detected by a temperature sensor is less than a reference exhaust temperature and is within a reduced-cylinder operation allowable range in which a combination of the engine speed and the engine load is set in advance. The second sub-control computer deactivates a second cylinder group based on a command of the reduced-cylinder operation. The main control computer commands a first sub-control computer and the second sub-control computer to perform an all-cylinder operation when the coolant temperature detected by the coolant temperature sensor is less than the reference temperature, and the exhaust temperature detected by the temperature sensor is greater than or equal to the reference exhaust temperature or is out of the reduced-cylinder operation allowable range in which a combination of the engine speed and the engine load is set in advance.