Oxygen concentration detector and method of using same

An oxygen concentration detector, comprising:

• an air-fuel ratio sensor;
• a heater that heats the air-fuel ratio sensor;
• and
• a heater controller that supplies electric power to the heater such that the air-fuel ratio sensor reaches an activation temperature;
• wherein the heater controller predicts whether an element of the air-fuel ratio sensor may be wetted, and limits the supply of electric power to the heater when wetting of the element is predicted.

A method of attenuating thermal shock of an element of an air-fuel ratio sensor disposed in an exhaust passage of an internal combustion engine, the method comprising:

• supplying electric power to a heater so as to heat the air-fuel ratio sensor disposed in the exhaust passage of the internal combustion engine to an activation temperature;
• detecting the temperature of the element of the air-fuel ratio sensor;
• detecting a rate of decrease in the temperature of the element of the air-fuel ratio sensor;
• determining, when the rate of decrease in the temperature of the element is greater than a reference value, that the element has been wetted;
• and
• controlling the supply of electric power to the heater so as to attenuate thermal shock of the element.

A method of attenuating thermal shock of an element of an air-fuel ratio sensor disposed in an exhaust passage of an internal combustion engine, the method comprising:

• supplying electric power to a heater so as to heat the air-fuel ratio sensor provided in the exhaust pipe of the internal combustion engine to an activation temperature;
• determining whether an element of the air-fuel ratio sensor may be wetted;
• and
• limiting the supply of electric power to the heater when it is determined that the element of the sensor may be wetted.