Air-fuel ratio detection device and air-fuel ratio detection method

A method of detecting an air-fuel ratio of exhaust gas using a sensor element including a sensor cell, the method comprising:

• applying voltage to the sensor cell,
• detecting an output current of the sensor cell,
• detecting or calculating a temperature correlation parameter correlated with a temperature of the sensor element, and
• calculating the air-fuel ratio of the exhaust gas based on the output current and the temperature correlation parameter.

An air-fuel ratio detection device comprising:

• a sensor element including a sensor cell;
• a voltage application circuit applying voltage to the sensor cell;
• a current detector detecting an output current of the sensor cell;
• and
• a control device, wherein
• the control device is configured to calculate an air-fuel ratio of an exhaust gas and detect or calculate a temperature correlation parameter correlated with a temperature of the sensor element, and
• the control device is configured to calculate the air-fuel ratio of the exhaust gas based on the temperature correlation parameter and the output current detected when a predetermined voltage is applied to the sensor cell.