Control system for cylinder cut-off internal combustion engine

Abstract

In a control system for an internal combustion engine having a plurality of cylinders whose operation of the engine can be switched between full-cylinder operation during which all of the cylinders are operative and cut-off-cylinder operation during which some of the cylinders are non-operative, and running control, i.e., either cruise control during which the vehicle is controlled to run at a desired vehicle velocity or preceding vehicle follow-up control during which the vehicle is controlled to run at a desired vehicle velocity to maintain a desired inter-vehicle distance from a preceding vehicle, is performed in response to an instruction of an operator, it is judged whether a velocity error between a detected vehicle velocity and the desired vehicle velocity and load of the engine are equal to or smaller than corresponding threshold values. If the result is affirmative when the running control is in progress, it is determined that running condition of the vehicle is stable and the engine operation is switched to the cut-off-cylinder operation, thereby preventing a control hunting from happening, while ensuring to improve fuel consumption by utilizing the cut-off-cylinder operation as much as possible.