Abstract: A fusing unit for an image forming apparatus has a heating roller, and a fusing belt assembly that rotates in contact with the heating roller. The fusing belt assembly comprises a pressure roller, a separating roller and a fusing belt rotatably supported by the pressure roller and the separating roller. A slip prevention element prevents slippage of the fusing belt. Because the slip prevention element is disposed at both ends of the separating roller so that it does not interfere with the paper sheet being fused, the quality of printing can be improved without shortening the life of the fusing belt.

Abstract: A fixing device includes a heating roller, a pressing roller, a fixing belt for forming a fixing nip, and a belt pressing member which slidably supports and presses the inner circumferential surface of the fixing belt in the entire fixing nip. Since a fixing nip can sufficiently expand and a time that a printable medium passes through the fixing nip can increase, a fixing temperature can be lowered while maintaining image fixing quality, and power consumption and a warming-up time can be reduced. In addition, looseness of the fixing nip due to an air gap can be prevented and thus good image fixing quality can be ensured.