PURPOSE: To prevent previously misfire caused upon switching and engine stall, by a method wherein a means, deciding that the revolution number of an engine is lower than a predetermined revolution number and stopping the switching of the number of operating cylinders is provided, when the number of operating cylinders is switched in accordance with the load of the engine.
CONSTITUTION: Even if an operating condition such as the load or the like is deviated from a partial cylinders operation zone, it is limited that the partial cylinders operation is returned to an all cylinders operation only when the revolution number N is higher than a preset revolution number N3, while, in the other cases, the partial cylinders operation is continued and the switching of the number of operating cylinders is not effected even if the output of an AND circuit 31 which is the set input of a flip flop 33, is switched from H to L. On the contrary, when the all cylinders operation is shifted to the partial cylinders operation, if the other conditions for the partial cylinders operation are satisfied, the switching of the cylinder number is never effected since the output of the AND circuit 31 which is the set input of the flip flop 33 is always on the L level in the zone in which the engine revolution number N is lower than the preset revolution number N3.
ISHIZAWA SHIZUO
AIHARA HISAMOTO
KAMEGAYA SHIGERU
NAKATSURU KAZUHIRO
