| 摘要 |
PURPOSE:To perform the positioning between an image carrier and the developing roller of a developing device with good precision and good reproducibility and to simplify the structure by composing a positioning member of a conductor and applying a developing bias to the developing roller through the positioning member. CONSTITUTION:Positioning plates 79a and 79b are fitted to a main frame 30 and V-shaped notches 81 and 81 are formed in the plates at one end. When a developing devices 27a or 27b is set at a development position, the shaft 78 of a magnet roller 77 abuts on the cut 81 to perform the positioning between a photosensitive drum 12 and the magnet roller 77. Further, the shaft 78 of the magnet roller 77 and the positioning plate 79b are made of conductors, and a holder 80 is made of an insulator; and a harness 84 for bias voltage supply is connected electrically to the positioning late 79a to supply a bias voltage only when one of developing devices 27a-27d is set at the development position. |
