CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

This control device for an internal combustion engine includes: an exhaust purification catalyst that is provided in an exhaust passage of the internal combustion engine; a downstream air-fuel ratio sensor 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.

主权项

1. A control system of an internal combustion engine, comprising an exhaust purification catalyst provided in an exhaust passage of the internal combustion engine; a downstream side air-fuel ratio sensor provided at said exhaust passage at a downstream side in a direction of flow of exhaust from said exhaust purification catalyst; and an air-fuel ratio control device which controls an air-fuel ratio of the exhaust gas flowing into said exhaust purification catalyst so as to become a target air-fuel ratio,
wherein said downstream side air-fuel ratio sensor is configured so that the higher the exhaust air-fuel ratio, the lower the applied voltage where the output current becomes zero, said applied voltage to the downstream side air-fuel ratio sensor is set to a voltage higher than the voltage where the output current becomes zero when the exhaust air-fuel ratio is the stoichiometric air-fuel ratio, when said target air-fuel ratio is richer than a predetermined reference air-fuel ratio, and is set to a voltage lower than the voltage where the output current becomes zero when the exhaust air-fuel ratio is the stoichiometric air-fuel ratio, when said target air-fuel ratio is leaner than said reference air-fuel ratio, and said reference air-fuel ratio is an air-fuel ratio of the stoichiometric air-fuel ratio or more.