| 摘要 |
PURPOSE:To detect a moment when a transfer material is inserted into the contact point between a photosensitive drum and a transfer means by arranging an optical sensor on a specific position in the drum. CONSTITUTION:The optical sensor 9 is arranged on a position opposed to a transfer roll 8 in the photosensitive drum 1 forming a photosensitive layer on a transparent supporting member. A toner image developed by toner supplied from a developing device 3 is rotated in an arrow direction. On the other hand, a transfer material is sent by a resist roller 6 at timing coincident with the leading end of the toner image and detected by the sensor 9 immediately before being inserted between the photosensitive body 1 and the roller 8, and at that time transfer bias power supply is impressed and transfer is started. Thereby, the transfer bias is impressed at the optimum timing.
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