Fixing device for an image forming apparatus with an ambient temperature sensor

摘要

In a fixing device (50) of an image forming apparatus (1) including a heating roller (51) and a temperature detecting device (52) spaced apart from the roller (51), having a first sensor (53) for detecting the surface temperature of the roller, and a second sensor (54) for detecting the ambient temperature, the first sensor (53) being placed at a first position in a casing (55) having an opening (56) through which the heat radiation of the roller (51) is directly incident and the second sensor (54) being enclosed by the casing (55) and placed at a second position to which the heat radiation of the roller (51) is not directly incident, the temperature is calculated on the basis of the outputs of the two sensors (53,54), and the opening (56) is disposed so as not to enter a region between the vertical plane containing the central axis (51c) of the roller (51) and a tangential plane to the circumferential surface of the roller (51) parallel to the vertical plane.