Patent ID: 8479494

Claim:
An exhaust gas sensor control system that controls energization of a heater that heats an exhaust gas sensor provided in an exhaust pipe of an internal combustion engine, the exhaust gas sensor control system comprising: an exhaust gas temperature sensor that detects an exhaust gas temperature of exhaust gas in the exhaust pipe; an air flow amount sensor that detects an air flow amount of air that is drawn into the internal combustion engine; an outside air temperature sensor that detects an outside air temperature; and at least one ECU programmed to function as: a condensed water amount estimating device that estimates an amount of condensed water that collects in the exhaust pipe using the exhaust gas temperature detected by the exhaust gas temperature sensor when the internal combustion engine is started, the air flow amount measured by the air flow amount sensor, and the outside air temperature detected by the outside air temperature sensor; a condensed water presence determining device that determines from the amount of condensed water estimated by the condensed water amount estimating device whether or not condensed water is present in the exhaust pipe; and a heater control device that supplies electric current to the heater if the condensed water presence determining device determines that there is no condensed water present in the exhaust pipe, wherein the condensed water amount estimating device calculates an estimated exhaust pipe wall temperature in the exhaust pipe, which is sequentially obtained using the exhaust gas temperature, the air flow amount, and the outside air temperature; calculates a dew-point of the exhaust pipe, which is determined based on an air-fuel ratio as a ratio of the air flow amount to the weight of fuel; obtains a relative exhaust pipe wall temperature based on the estimated exhaust pipe wall temperature and the dew-point; calculates a condensed water added amount based on the relative exhaust pipe wall temperature and the air flow amount; and estimates the amount of condensed water by summing the calculated condensed water added amount the condensed water amount estimating device estimates the amount of condensed water present upstream and downstream of the exhaust gas sensor in the exhaust pipe, the condensed water presence determining device determines whether the amount of condensed water estimated by the condensed water amount estimating device is present upstream of and downstream of the exhaust gas sensor, and a plurality of maps utilized to estimate the amount of condensed water present upstream of the exhaust gas sensor are different than those utilized to estimate the amount of condensed water present downstream of the exhaust gas sensor.