Patent ID: 8787780

Claim:
An image forming apparatus comprising: an image forming unit configured to form an image on a recording sheet; and a fixing unit comprising; an endless belt; a heater including a first resistance heating element and a second resistance heating element, the first and second resistance heating elements formed on a substrate and being in contact with an inner surface of the endless belt; a nip forming element that forms, together with the heater via the endless belt, a fixing nip for nipping and conveying a recording sheet having an image formed thereon, and a temperature detection unit that detects a temperature of the heater, the fixing unit capable of switching between a first operation mode in which the first resistance heating element and the second resistance heating element are connected in series and a second operation mode in which the first resistance heating element and the second resistance heating element are connected in parallel, wherein the image forming apparatus further comprises a current detection unit disposed in a conduction path after branching toward the first resistance heating element and the second resistance heating element in a parallel connecting state, wherein if a temperature increase rate detected by the temperature detection unit is less than a threshold rate, although a current detected by the current detection unit is greater than a threshold current, a notification of a failure is issued or a driving operation of the apparatus is stopped, and wherein the first resistance heating element is disposed on an upstream side in a recording sheet conveying direction with respect to the second resistance heating element, and the current detection unit detects a current in the first resistance heating element.