| 摘要 |
PROBLEM TO BE SOLVED: To stop the current conduction to a heating body before the temperature thereof becomes abnormally high and to prevent the heating body from being damaged by calculating the rising speed of the temperature of the heating body based on the output of a temperature detection element and stopping the current conduction to the heating body when the calculated value exceeds a fixed value. SOLUTION: The output of the temperature detection element 5 of every fixed time is fetched by a CPU 24 and the rising speed of the temperature is calculated by the CPU 24. Then, the calculated value is always compared with the previously set fixed value (reference value) for deciding the stop of the energizing. Since it is a normal time when the rising speed of the temperature calculated by the CPU 24 is smaller than the reference value, a normal temperature control action is executed. Since it is an abnormal time that excessive electric power is supplied to a resistance heating element 32 because of the short-circuit of a TRIACK 25 and the like when the rising speed of the temperature is larger than the reference value, a signal for cutting a relay 33 is outputted from the CPU 24 so as to stop the energizing of the element 32. Simultaneously, an error display is outputted so as to inform a user of the fault of a fixing device. Thus, the heating body 3 is prevented from being damaged.
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