Fixing device and image forming apparatus including same

An image forming apparatus comprising a fixing device,

• the 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.