US Patent 7661398 Control device and control method of internal combustion engine

An ECU executes a program including steps of estimating an oil temperature based on a water temperature sensed by a water temperature sensor, setting NE(1) to a lower limit value of an engine revolution speed NE when the oil temperature is equal to or higher than a threshold THO(0), setting NE(2) (NE(2)<NE(1)) to the lower limit value of engine revolution speed NE when the oil temperature is lower than the threshold THO(0), and controlling an engine driving an oil pump to keep the engine revolution speed NE equal to or higher than the set lower limit value.