FIXING DEVICE AND IMAGE FORMING APPARATUS

PROBLEM TO BE SOLVED: To provide an external IH system fixing device capable of preventing the overheat of a high speed machine without increasing the size of the fixing device, and to provide an image forming apparatus. SOLUTION: The fixing device 100 of an external IH system includes an excitation coil 210 and heats a fixing roller 101 by electromagnetic induction. A main core 212 along which electromagnetic flux generated by the excitation coil 210 is guided to the fixing roller 101 has partial cores 212a to 212c. The partial cores 212a and 212c slide in the direction of the rotation axis of the fixing roller 101 by a screw feed mechanism driven by a pulse motor 403. In accordance with the width of recording paper passing through the fixing device 100, the partial cores 212a and 212c are slid. In addition, the overheat of an area through which paper is not passed is prevented by turning on/off excitation coils 211a and 211b. COPYRIGHT: (C)2010,JPO&INPIT