Patent ID: 8346106

Claim:
A fixing device for fixing an unfixed toner image on a recording medium with heat and pressure, comprising: a fixing member including a recording medium passing area inside the fixing member through which the recording medium passes; a first heater disposed inside the fixing member, to heat the fixing member; a first pressing member disposed opposite the fixing member to press against and rotate the fixing member to define a fixing nip through which the recording medium bearing the unfixed toner image passes to fix the unfixed toner image; a second heater disposed outside the recording medium passing area and inside the fixing member, to heat a uniform region of the fixing member cyclically in a given cycle of heating such that a temperature of the second heater is increased and decreased cyclically which heats the fixing member cyclically; a temperature detector to detect a change in temperature of the fixing member when the fixing member is cyclically heated by the second heater while the fixing device is in operation; and a determination unit to evaluate a condition of rotation of the fixing member based on a comparison between the cycle of heating by the second heater and the change in the temperature of the fixing member detected by the temperature detector.