Air-fuel ratio control system

In a system for controlling the air-fuel ratio control for an internal combustion engine of the type having a carburetor with an intake passage, air-fuel mixture supply means for supplying an air-fuel mixture to the intake passage, an exhaust passage communicating with the engine, a throttle valve in the intake passage, detecting means for detecting the concentration of a constituent of exhaust gases passing through said exhaust passage and producing an output signal dependent thereon, comparator means for comparing said output signal of said detecting means with a set value and producing an output signal dependent thereon, an integrating circuit and a proportional circuit connected to said comparator means, a driving circuit connected to said integrating and proportional circuits for producing an output signal in dependency on said output signal of said integrating and proportional circuits, an electromagnetic valve means actuated by the output signal of said driving circuit for correcting the air-fuel ratio of the air-fuel mixture supplied by said air-fuel mixture supply means, throttle sensing means for detecting the operation of said throttle valve and producing an output signal dependent on the magnitude of acceleration and deceleration respectively of said internal combustion engine, and a circuit for varying the constant of said integrating and proportional circuits, the improvement comprising

• differentiating circuit means for differentiating the output signal of said throttle sensing means and for producing an output signal dependent on said acceleration and deceleration, respectively,
• rectifier means for rectifying said output signal of said differentiating circuit means, and
• semiconductor element means, having a resistance which varies with a variation of voltage applied thereto, for increasing the constants of said integrating and proportional circuits with an increase in the output signal of said rectifier means.