| 摘要 |
PURPOSE:To advance a time point of operation of a thermosensible breaker and to protect a heat roller, etc., from damage caused by overheating, by reducing an overshoot of a surface temperature of the heat roller. CONSTITUTION:A thermistor TH which contact or stands close to the surface of a heat roller 32h detects a surface temperature T1 of the heat roller 32h, and it is concerned in turn-on and turn-off of a heater H. A pressure roller 32p is separated from the heat roller 32h except the time of copying operation, and pressed against the heat roller 32h at the time of copying operation and rotated together with the heat roller 32h. When the surface temperature of the heat roller 32h becomes an abnormally high temperature, a temperature fuse F operates, cuts off an electric conduction line of the heater H and obstructs abnormal overheating of the heat roller 32h. An operating temperature of this temperature fuse F is correlated to the surface temperature T1 of the heat roller 32h, and also, is determined so as to be related to an extended operation time of a main motor M1 and/or an exhaust fan motor M5 for driving a fixing device 32.
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