| 摘要 |
PROBLEM TO BE SOLVED: To keep the quantity of a current to a heater constant by carrying on processing, without causing an error as much as possible and holding control over the current to the heater equally to normal phase control. SOLUTION: The image forming apparatus is equipped with the heater which thermally fixes an unfixed image on a sheet, an AC power source which supplies electric power to the heater, a means of detecting the timing of zero crossing where the AC source voltage becomes zero, a means of detecting the temperature of the heater, a phase control means of switching from ON-state where the electric power is supplied to the fixing heater to OFF-state wherein the electric power is not supplied and vice versa within a half cycle of the AC power source so that the heater temperature reaches a designated value, and a timer means; and the timer, means generates a reference timer having the same interval as interval of zero crossing and when the interval of zero crossing exceeds the reference timer value, the supply of the fixing heater electric power which is in the ON-state in the time-out timing of the reference timer is switched to the OFF-state. COPYRIGHT: (C)2006,JPO&NCIPI
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