| 摘要 |
PURPOSE:To prevent the occurrence of abnormal temp., etc. owing to the disconnection, short-circuiting, etc. of the connector interposed between a temp. control body and a setting means by changing the gain of a noninversion amplifier from the outside thereby changing the set reference voltage of a comparator for temp. controlling. CONSTITUTION:As the feedback resistances R5, R6, R7 of a noninversion amplifier 10 of a voltage follower are selected by the switches S1, S2 of a temp. change-over part 12, the gain of the amplifier 10 changes, and according to the operations of the switches S1, S2, the output voltage of the amplifier 10 is changed over to 3 stages. The changed over voltage as reference voltage is compared with the voltage corresponding to the detection temp. of a fixing device by a thermocouple 1 and an amplifier 10, in a comparator 3, by which the on-state of the heater of the fixing device is controlled. When this temp. control device is isolated from a temp. setting change- over device 12 and a connector for relaying is interposed, the disconnection and short-circuiting of the connecting wires are equivalent to the on-and off-states of the switches S1, S2 so that the occurrence of abnormal temp. is prevented. If a capacitor 13 is provided, the induction and noise by an AC power source are eliminated. |
