CONTROL DEVICE FOR AN INTERNAL COMBUSTION ENGINE

This control device for an internal combustion engine includes: an exhaust purification catalyst (20) that is provided in an exhaust passage of the internal combustion engine; a downstream air-fuel ratio sensor (41) that is provided downstream of the exhaust purification catalyst; and an air-fuel ratio control device that controls such that the air-fuel ratio of exhaust gas flowing into the exhaust purification catalyst reaches a target air-fuel ratio. The downstream air-fuel ratio sensor is configured such that the applied voltage thereof at which the output current becomes zero decreases as the exhaust air-fuel ratio increases. If the target air-fuel ratio is richer than the reference air-fuel ratio, the voltage applied to the downstream air-fuel ratio sensor is set to a higher voltage than the voltage at which the output current becomes zero when the exhaust air-fuel ratio is the stoichiometric air-fuel ratio. If the target air-fuel ratio is leaner than the reference air-fuel ratio, the voltage applied to the downstream air-fuel ratio sensor is set to a lower voltage than the voltage at which the output current becomes zero when the exhaust air-fuel ratio is the stoichiometric air-fuel ratio. A control device for an internal combustion engine using an air-fuel ratio sensor that can reliably detect when the absolute value of the exhaust air-fuel ratio reaches a prescribed air-fuel ratio richer than the stoichiometric air-fuel ratio is thus provided.