| 摘要 |
<P>PROBLEM TO BE SOLVED: To shut off the feeding of power in times of abnormality, to prevent receiving any damage due to smoking or heat when the fixing device is actually in an excessively heated state and to realize space saving in a control substrate and bringing down of the cost by improving the precision in detection time in an output shorted-circuited state of a triac controlling a heating means in a fixing device. <P>SOLUTION: The feeding and shutting off of power to the heat fixing roller 21 is changed over by the triac 173, the temperature is detected by a thermistor 32 and the temperature of a fixing roller 21 is controlled to a specified temperature by a controller 100. Then, in a safety circuit 200, the edge interval of the state detecting signal of power feeding to the fixing roller 21 is measured when the control signal to the triac 173 is in a power shut off state. An abnormal signal is outputted when judgement is made that the measured edge interval is longer than a first set time. Furthermore, continuous output of the abnormal signal for more than a second set time is measured and the control signal to the triac 173 is set from these results. <P>COPYRIGHT: (C)2004,JPO |
