| 摘要 |
PURPOSE:To prevent a photosensitive body and a developing roller from damaging by providing the developing roller to the photosensitive body so that they contact and leave each other and separating the developing roller from the photosensitive body when toner decreases below a specific amount and a toner end signal is outputted. CONSTITUTION:When the amount of toner in a hopper 4 is larger than the specific value, a changeover cam 18 is separated from a pressure lever 16 and the developing roller 3 is pressed against the surface of the photosensitive body 1 with the elastic force of a pressure spring 17. When the toner decreases in amount below the specific value as development advances, that is detected by a toner end sensor 21. Consequently, a detecting circuit 22 outputs the toner end signal to a motor drive control circuit 20 to allow the cam 18 to make a half turn. Then, the lever 16 swings clockwise to oscillate the hopper 4 counterclockwise around a pivot 12 through a guide rail 14. Consequently, the developing roller 3 is moved to leave the photosensitive body 1. When toner is all consumed, the developing roller 3 leaves the photosensitive body, so the developer roller 3 having no toner layer never presses the photosensitive body 1 directly and their surfaces to not damage each other. |
