Patent ID: 7104244

Claim:
A control system for a variable-cylinder internal combustion engine which is operated by switching an operation mode between an all-cylinder operation mode in which all of a plurality of cylinders are put in operation and a partial-cylinder operation mode in which some of the plurality of cylinders are deactivated, comprising: load-detecting means for detecting load on the engine; first switching determination means for determining that the operation mode should be switched to the all-cylinder operation mode, when the detected load on the engine is larger than a first reference value, during the partial-cylinder operation mode; degree-of-continuation parameter-calculating means for calculating a degree-of-continuation parameter indicative of a degree of continuation of a state where the load on the engine is within a predetermined range of load between the first reference value and a second reference value smaller than the first reference value, during the partial-cylinder operation mode; second switching determination means for determining based on the calculated degree-of-continuation parameter whether or not the operation mode should be switched to the all-cylinder operation mode; and switching execution means for executing switching from the partial-cylinder operation mode to the all-cylinder operation mode based on results of determinations by said first switching determination means and said second switching determination means.