| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a high reliablity and capable of speedily and securely detecting the disconnection of a thermister being a temperature detection element for detecting the surface temperature of a fixing roller. <P>SOLUTION: The energization and temperature control of the heater of the fixing roller is started, a distance M between the thermister and the fixing roller is inputted, the value Y detected by a temperature sensor which detects the temperature of the environment is read, the initial value R1 of the resistance value of the thermister is read, and a period TA is set as a disconnection detection period Z (P11 to P15). The resistance value R2 of the thermister at the time is read (P17). A difference between R1 and R2 and a specific value B which is the reference value for detecting the disconnection of the thermister, ((R2-R2)>B), is repeatedly determined (P19). If the difference is larger than the value B, the thermister is determined to be normal and processing is terminated. If (R2-R1) is lower than the value B, it is determined whether the period TA set as the disconnection detection period has elapsed or not (P21). If the period TA has elapsed, the thermister is determined to be in an abnormal state (disconnection). Then, the supply of power to the heater is shut off and warning is displayed (P23). <P>COPYRIGHT: (C)2005,JPO&NCIPI |
