Patent ID: 8805260

Claim:
A fixing device comprising: a fixing roller configured to be heated by a heat source; and a pressure roller configured to be in pressure-contact with the fixing roller, wherein the fixing roller includes a cylindrical tubular core having an inner circumferential surface and at least one spiral rib protruding from the inner circumferential surface and extending spirally along the inner circumferential surface, and the total number of times that the at least one spiral rib crosses through a region of contact between the fixing roller and the pressure roller is more than one, regardless of a rotation angle of the fixing roller, wherein the at least one spiral rib has a lead angle at an axial middle region of the fixing roller smaller than a lead angle at an axial end region of the fixing roller, wherein the lead angle is an angle of the at least one spiral rib with respect to a plane extending orthogonal to an axis of the cylindrical tubular core.