Patent ID: 8811837

Claim:
A fixing device comprising: a substantially cylindrical metal member; a heater positioned to heat the metal member; an endless, flexible fixing member disposed rotatably around the metal member, an inner circumferential surface of the fixing member being heated by the metal member to heat and fix a toner image; a rotary pressing member disposed opposite and parallel to the metal member and pressed against an outer circumferential surface of the fixing member to form a nip between the rotary pressing member and the fixing member through which a recording medium bearing the toner image passes; a stationary member disposed at an inner circumferential surface side of the fixing member and pressed by the rotary pressing member via the fixing member to form the nip; a first temperature detector disposed upstream from the nip in a rotation direction of the fixing member to detect a surface temperature of the fixing member; and a second temperature detector disposed downstream from the nip in a rotation direction of the rotary pressing member to detect a surface temperature of the rotary pressing member, wherein, when a difference between a surface temperature of the fixing member detected by the first temperature detector and a surface temperature of the rotary pressing member detected by the second temperature detector after a predetermined time has elapsed since the first temperature detector detects the surface temperature of the fixing member is greater than a predetermined threshold, the heater stops heating the metal member.