| 摘要 |
PURPOSE:To detect effectively presence/absence of a form even if a carrying path has a high temperature, by generating a certain electric field in the carrying path of the form and detecting variation of this electric field. CONSTITUTION:A corotron 10 and a plate electrode 20 as a detecting part of a form PA are arranged before a fixing device 6 so that they face each other with the carrying path of the form PA between themselves, and a high voltage is impressed to the corotron 10 from a power supply circuit 31, and a plate current Ip is generated in the electrode 20 by a strong electric field and is fed back to a high voltage transformer 32. When the form PA reaches the detecting part, the current Ip is reduced. This reduced voltage is subjected to waveform shaping by a waveform shaping circuit 42 and is applied to a comparator 60; and if this voltage is lower than reference voltage of a reference voltage setting circuit 50, the form PA is detected. On a basis of this detection signal DS, a CPU70 executes a prescribed processing. |
