Idling speed control device of an internal combustion engine

An idling speed control device of an internal combustion engine having an intake passage and a throttle valve arranged in the intake passage, said device comprising:

• a bypass passage interconnecting the intake passage located upstream of the throttle valve to the intake passage located downstream of the throttle valve;
• valve means arranged in said bypass passage and having a control valve controlling a flow area of said bypass passage;
• a step motor for controlling the amount of air flowing within said bypass passage in accordance with a change in the operating condition of the engine at the time of idling, said step motor comprising a motor housing, a stator stationarily arranged in said motor housing, and a rotor rotatably arranged in said motor housing;
• a valve shaft axially movable in said motor housing and actuated by said rotor, said control valve being fixed onto said valve shaft, said rotor being rotatably mounted on said valve shaft;
• and
• transforming means, including said rotor and operatively coupling said rotor and said valve shaft, for transforming the rotation motion of said rotor to the axial movement of said valve shaft.