Patent ID: 8265495

Claim:
A heating device comprising: a driving member configured to be driven by a driver and to rotate; a driven member being in contact with the driving member and configured to rotate with the rotation of the driving member; a heater configured to heat a surface of at least one of the driving member and the driven member; a temperature detector configured to measure the temperature of the heated surface; and a controller operable to control heating of the heater based on the measurement result of the temperature detector, the controller comprising: a calculator operable to calculate a change ratio of a slope of a temperature change of the heated surface with time, based on a first temperature detected by the temperature detector at a first time point and a second temperature detected by the temperature detector at a second time point, the second time point being a time point when a predetermined time has elapsed from the first time point; and a determiner operable to determine that an abnormality occurs when the change ratio exceeds a threshold.