IDLING ROTATIONAL SPEED CONTROL METHOD FOR INTERNAL COMBUSTION ENGINE AND ITS CONTROL DEVICE

PURPOSE:To prevent an engine from causing an engine stop, by installing an air flow securing means for controlling an idling rotational speed control valve in a position where a given minimum air flow required for operating an engine is supplied, when a driving force is not provided from an output unit to drive said valve. CONSTITUTION:In an idling rotational speed control device 14, which is installed in a bypass passage by passing a throttle valve, and located in a throttle valve chamber disposed in an intake passage, an air passage 20 connecting to said bypass passage is formed in said valve body 21. This air passage 20 is allowed to be opened by forcing a plunger 18 to advance to the right against a spring 24 because of the energization of a solenoid mechanism 19 and permitting a valve 30 to move integral therewith. In such construction, internal bypass 27, 28 are formed additionally in parallel to the air passage 20 in the valve body 21 so as to enable a required minimum air to be secured in an emergency when the shutoff of a drive current to a coil 16 has caused the valve 30 to return to its initial position, and thereby an engine can be kept free from its stop.