| 摘要 |
A system for controlling the air-fuel ratio for an internal combustion engine having an intake passage, an exhaust passage, a detector such as an oxygen sensor for detecting the concentration of oxygen in the exhaust gases, an air-fuel mixture supply unit, an on-off type electromagnetic valve for correcting the air-fuel ratio of the air-fuel mixture supplied by the air-fuel mixture supply unit, and an electronic control circuit for producing square wave pulses in dependency on the output signal from the detector for driving the on-off type electromagnetic valve. The system comprises a venturi for producing a vacuum dependent on rapid acceleration, a vacuum sensor for sensing the vacuum in the venturi at rapid acceleration of the internal combustion engine and producing an output signal dependent thereon, an intake opening in the venturi for communicating the vacuum with said vacuum sensor, pulse width modulator for producing a pulse width modulating signal when an output signal of the vacuum sensor rises above a predetermined level at a rapid acceleration, the pulse width modulator being connected to the electronic control circuit, such that said pulse width modulating signal is fed to said electronic control circuit for modulating the width of said square wave pulses in dependency on the rapid acceleration for enriching the air-fuel mixture.
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