Fixing device, image forming apparatus, and method for adjusting length of interposing and pressurizing region by fixing device

An image forming apparatus comprising:

• a transfer unit configured to transfer a toner image onto a sheet;
• and
• a fixing device configured to fix the toner image onto the sheet, the fixing device including:
• an endless belt;
• a pressure element configured to convey the sheet under pressure with endless belt;
• a heating member provided on an inner side of the endless belt and configured to heat the endless belt;
• an adjustment mechanism configured to move at least one of the heating member and the pressure element so as to adjust a nip width, which is a length of an interposing and pressurizing region in a sheet conveyance direction, the interposing and pressurizing region being formed by the heating member and the pressure element with the endless belt under pressure therebetween;
• and
• a controller configured to control the adjustment mechanism so that A>B is satisfied, where A is a nip width during a fixing process in which the sheet is heated to fix the toner image onto the sheet, and B is a nip width during temperature raising of the heating member before the fixing process.