Patent ID: 8811842

Claim:
A fixing device comprising: a fixing rotary member having a heating layer; a pressure rotary member configured to form a nip while contacting the fixing rotary member and rotate to drive the fixing rotary member; a temperature detector to detect a temperature on a circumference of the fixing rotary member; and an excitation coil provided near the fixing rotary member and configured to induction-heat the heating layer of the fixing rotary member based on a detection result from the temperature detector, wherein, when the fixing device is in a standby time during which time the fixing rotary member continues to rotate, a rotation speed of the fixing rotary member is changed and controlled to maintain a target temperature when a periodic temperature difference, occurring on the circumference of the fixing rotary member, has a fluctuation amplitude larger than a predetermined value compared to the target temperature, wherein the rotation speed of the fixing rotary member is changed in a standby time in which the fixing rotary member, while rotating, is heated and controlled to maintain a target temperature when a detected temperature T of the fixing rotary member detected by the temperature detector attains a target temperature Tref for the fixing rotary member, and a number of times that formula (1) is satisfied exceeds a predetermined number during a predetermined time period: | T−T ref|≧Δ T, (1) where ΔT is a predetermined difference in the temperature, wherein the rotation speed of the fixing rotary member is changed so as to satisfy a relation S>L×4, and wherein S (sec) is a rotation cycle of the fixing rotary member, and L (sec) is a response speed for heating control of the fixing rotary member.