PURPOSE: To prevent carburetor air control electro-magnetic valves from a resonance by changing an operating frequency of the electro-magnetic valves on the basis of a revolution number of an engine.
CONSTITUTION: Receiving an ignition pulse 22 from an engine 2, a revolution number sensor 20 converts a revolution number into an electric signal. Signals of the sensors 19, 20 are inputted into a control circuit 21. By opening or closing electro-magnetic valves 14, 15 at a certain duty ratio in response to signals which are generated from the control circuit 21, a proper amount of air is additionally supplied for a fuel system via air regulation passages 8, 13 and air bleeds 7, 12 to control an air fuel ratio. An output of the revolution number sensor 20 is transmitted to a corrective signal generating circuit 28, which sends a signal to a triangular wave generation circuit 26 for changing an oscillated frequency, thereby avoiding a resonance frequency of the electro-magnetic valves generated by revolution of an engine.
NAKAMURA MITSUO
DAISHIN MASAAKI
KATAOKA RIYUUJI
NISSAN MOTOR