Control apparatus and control method for internal combustion engine

A control apparatus for an internal combustion engine, which is employed for a multi-cylinder internal combustion engine that includes a camshaft provided to press engine valves against reaction force of valve springs;

• a hydraulically-actuated variable valve operating mechanism which changes a valve characteristic of the engine valves by changing a rotational phase of the camshaft relative to a crankshaft;
• and a valve stop mechanism which stops opening and closing of the engine valve(s) in a part of cylinders, the control apparatus executing a variable valve control that makes an actual value of the valve characteristic match a target value of the valve characteristic by executing a hydraulic pressure control for the variable valve operating mechanism, and the control apparatus operating the valve stop mechanism so that a reduced-cylinder operation is performed when an engine operating state is in a preset reduced-cylinder operation region, wherein
• if it is determined that a pressure of hydraulic fluid supplied to the variable valve operating mechanism is equal to or lower than a preset determination pressure when the engine operating state is in the reduced-cylinder operation region, the control apparatus prohibits the reduced-cylinder operation,
• wherein the preset determination pressure is variably set so that the preset determination pressure is increased as a temperature of the hydraulic fluid increases.