PURPOSE: To make optimum changing-over from the non-EGR control to EGR control and vice versa.
CONSTITUTION: The final target step number EGSTPD of a stepping motor for driving an EGR valve is determined (S10) on the basis of the EGR damper factor EGRDMP (S9) which is set according to the instant cut condition (S1) and slow cut condition (S4) and gradually altered during changing-over from the non-EGR control to EGR control or vice versa, and the degree of opening of EGR valve is controlled (S11) with this target step number EGSTPD. Thus the changeover speed from the non-EGR control to EGR control or vice versa can be altered according to the instant cut condition and slow cut condition, so that it is possible to make optimum the changeover between the non-EGR control ad EGR control while output stepping, stall, etc., are suppressed.
KONO AKIHIRO
NAGAISHI HATSUO
