HEAT FIXING DEVICE

PURPOSE:To shorten a preheating time by installing a plate type heating body which has length corresponding to the axial length of a fixation roll on the reverse surface of a guide member. CONSTITUTION:Heat rolls 1 and 2 use small-diameter, thin metallic hollow cores so as to decrease in thermal capacity. Further, the plate type heating body 12 which is nearly as long as the heat rolls is installed facing a paper feed guide 4. When a base 5 which holds a tone image 6 is conveyed as shown by arrow, the base moves along the paper feed guide 4 toward the press-contacting part of the heat rolls 1 and 2. At this time, the heating body 12 is supplied with electric power to heat the toner image 6 at temperatures above the softening point of the toner. Consequently, the toner image 6 enters a semifused state before fixation, so the image is fixed excellently with a short preheating time. Thus, the preheating time is shortened.