| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which temperature control can be exerted as intended even when the frequency of an AC power source is changed. <P>SOLUTION: The image forming apparatus includes: a zero-cross detecting means for comparing a voltage from a power source with a predetermined threshold, outputting a positive signal when the voltage is higher than the threshold, and outputting a negative voltage when the voltage is lower than the threshold; a pulse width detecting means for detecting pulse widths of the positive and negative pulse widths; and a heat fixing device that heats an image formed on a recording material, thereby fixing it to the recording material. The image forming apparatus exerts frequency control for the supply of power to the heat fixing device. The image forming apparatus controls the supply of power to the heat fixing device: at a second timing after a first predetermined time determined based on the positive pulse width is elapsed from a first timing at which the zero-cross signal is changed from the negative pulse width to the positive pulse width; and a fourth timing after a second predetermined time determined based on the negative pulse width has elapsed from a third timing at which the zero-cross signal is changed from the positive pulse width to the negative pulse width. <P>COPYRIGHT: (C)2007,JPO&INPIT |
