. "FIG. 8B is a side view of the heating roller 23 when the internal core 23A and the shield members 23B are rotated by a reference angle from positions of the internal core 23A and the shield members 23B illustrated in FIG. 8A. As illustrated in FIGS. 8A and 8B, the internal core 23A includes a small-diameter portion 23A1 and/or large-diameter portions 23A2." . . .