PURPOSE: To reduce a number of part items for a device and its cost, by directly or indirectly utilizing the amount of intake air per unit of every revolution for detection of speed at the time of deceleration and controlling pressure in an intake pipe not to excessively lower.
CONSTITUTION: Since pressure in the intake pipe of an engine is almost is proportion to the amount of intake air per every revolution displacement of the engine Q/N, for the ratio Q/N to become a preset value or less when the engine is decelerated, the duty ratio of a solenoid on-off valve 51 is changed to increase the flow amount of an air control valve 30, raise pressure at the time of firing in a combustion chambr of the engine, prevent misfiring, suppress a discharge amount of HC to the atmosphere and decrease a harmful component simultaneously control a catalyser reactor 71 not to be at not lower than its temperature of melting and damage. And the ratio Q/N is obtained by dividing the amount of intake air Q measured in an air flow meter 12 with speed of the engine N detected in an ignition distributor 18.
SUEISHI MOTOHARU
YAMAZOE HISAMITSU
