Patent ID: 7526914

Claim:
A heater control device for a gas sensor which includes a sensor element for detecting density of a specific component in a gas and a heater for heating the sensor element and is located downstream of an exhaust gas purifying device in an exhaust pipe for an in-vehicle engine to control power supply to the heater in such a manner as to make the sensor element at a predetermined active state, comprising: heat calculating means which calculates heat data corresponding to a heat budget in the exhaust pipe at a vicinity of the gas sensor after engine startup based upon an operating condition of an engine and a driving condition of a vehicle; determination means which makes a determination as to dryness inside the exhaust pipe based upon the calculated heat data, the determination means comprising: wall temperature calculating means which calculates an exhaust pipe wall temperature at a vicinity of the gas sensor based upon the heat data; dew point temperature calculating means which calculates a dew point temperature at a vicinity of the gas sensor based upon a state inside the exhaust pipe; and dry state determination means which compares the exhaust pipe wall temperature with the dew point temperature to determine a dry state inside the exhaust pipe; limit means which limits the power supply to the heater based upon the result of the determination as to the dryness by the determination means; and estimating means which estimates oxygen concentration inside the exhaust pipe based upon the operating condition of the engine, wherein: the dew point temperature is calculated based upon the estimated oxygen concentration.