Fusing unit and image forming apparatus using the same

A fusing unit which is formed on a printing path of an image forming apparatus and fuses an image to a printing medium, the fusing unit comprising:

• a heat source;
• a nip plate which is heated by the heat source, and comprises a nip part to heat and press the printing medium;
• a reflection member including a heat reflecting surface which is formed on a side of the nip plate and reflects heat generated by the heat source toward the nip part;
• a belt member which is rotatably provided about the heat source, the nip plate and the reflection member, and guides the movement of the printing medium;
• and
• a driving roller, which faces the nip part to form a fusing nip between the nip part and the driving roller corresponding to a width of the nip part, disposed such that the belt member is between the nip plate and the driving roller, and the driving roller rotatably drives the belt member,
• wherein the heat reflecting surface of the reflection member satisfies a curvature condition according to Formula 1, Formula 1 being φ/2-15°≦θ≦φ/2+15°, where L1 is a straight line between an arbitrary position on the reflection member and a center of the heat source, L2 is a straight line which crosses the arbitrary position on the reflection member and is vertical to the nip part, φ is an obtuse angle formed between the straight lines L1 and L2, and θ is an acute angle formed between a line tangent to the reflection member at the arbitrary position on the reflection member and the straight line L1.