Patent ID: 7606508

Claim:
An image forming apparatus, comprising: a fixing roller having a rotating heating section; an endless fixing belt rotated together with the fixing roller; a pressurizing section arranged on an inner peripheral surface side of the fixing belt, wherein the pressurizing section presses the fixing belt for being in pressure contact with the fixing roller, and corresponding to an outer peripheral surface of the fixing roller, the pressurizing section is deformed into a concave shape together with the fixing belt, wherein the pressurizing section forms a first nip portion between the fixing roller and the fixing belt; a separation section arranged downstream of the pressurizing section in a conveyance direction of a recording material and arranged in the inner peripheral surface side of the fixing belt, wherein the separation section presses the fixing belt for being in pressure contact with the fixing roller wherein by a tip of the separation section, the outer peripheral surface of the fixing roller is deformed into a concave shape, wherein the separation section forms a second nip portion between the fixing roller and the fixing belt, and wherein a toner image on the recording material is fixed at the first nip portion and the second nip portion; and a controller for controlling a pressing force of the separation section so that when an envelope is passed through as the recording material the pressing force becomes stronger than the pressing force when a plain paper passes through as the recording material.